Bridging Internetwork Operating System Release 10.2

Internetwork Operating System Release 10.2

cisc EM Bridging

Software Release O2 September 1994

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Bridging

Chapter Bridging Overview 1-1

Chapter Transparent Bridging 2-1

Chapter Source Route Bridging 3-1

Chapter Mixed-Media Bridging 4-1

Chapter Remote Source-Route Bridging 5-1

Cisco Systems Inc 1994 Table of Contents iii iv Bridging ver 10.2 CHAPTER

Brdgng Overview

Cisco Systems Inc 1994 Bridging Overview 1-1 Objecflves

Upon compeflon of this modue you wUH be abHe to perform the foUowng tasks

Describe the basic functions of bridge

Identify the various bridge types supported by Cisco

Describe when to implement each of the bridge types

1994 12 Bridging Cisco Systems Inc Routing and Bridging

RoutabHe Protocos

NonroutabHe ProtocoHs

FRAME

Routing is based on the logical addresses contained in the network layer of the OSI reference model

routable protocol may be routed or in some cases it may be bridged

such Some protocols as LAT Local Area Transport and MOP Maintenance Operation Protocol and NetBIOS have no logical addressing and therefore cannot be routed The nonroutable protocols

must be bridged

Cisco Systems Inc 1994 Bridging Overview 1-3 NonRoutabe Protocos

Routed Routed

Bridged Bridged

Nonroutabe protocos must be brdged

station using routable protocol

station using bridgable-only protocol

Cisco Inc 1994 1-4 Bridging Systems SourceRoute Brdgng

Uses RFs to define path to desfinaflon

Hosts must support SRB

Source-Route Bridging SRB

Specifies communication between two token rings

Path information is carried in RIF

Path information is gathered by an explorer packet

Cisco Systems Inc 1994 Bridging Overview 15 Transparent Bridging

Brdge transparent to hosts

defines the connection of two Ethernet domains Transparent Bridging

Cisco Systems Inc 1994 16 Bridging EncapsuNated Brdgng

Brdge frames are passed over Sera or FDD

Encapsulated Bridging provides for the encapsulation of transparently bridged frames over wide-area network WAN and local-area network LAN links such as FDDI

Encapsulated bridging sometimes referred to as remote transparent bridging

Cisco Systems Inc 1994 Bridging Overview 1-7 SRT and SRITLB

SRT Source Route Transparent Simultaneous Source Route and Transparent Bridging

SRITLB Source Route Translational Bridging Translates between Source Route and Transparent Bridging

Source-Route Transparent Bridging SRT

Defines source-route bridging as an option on top of transparent bridging

transfer Handles both source-route and transparent bridging at the same time one packet per

Keeps the Token Ring and Ethernet domains separate

Source-Route Translational Bridging SRITLB

Brings the Token Ring and Ethernet domains together

Enables device on Token Ring to communicate seamlessly with device on Ethernet

Routing is more common solution

Cisco 1994 1-8 Bridging Systems Inc Remote Source Route Bridging

Token cAll Token\

Arbätrary mecila between SRBs

Remote Source Route Bridging RSRB

Provides serial tunneling of Token Ring frames

Enables Token Ring SRB frames to be encapsulated over an arbitrary media

Cisco Systems Inc 1994 Bridging Overview 1-9 Summary

TB Transparent Bridging

No RIFS

SRB SourceRoute Bridging

RIFs

Token Ring Token Ring

SRT Source-Route Transparent Bridging

Ethernet Ethernet and Token Ring Token Ring

SR/TLB Source-Route Translational Bridging

Ethernet Token Ring

RSRB

Token Ring Arbitrary Media Token Ring

Cisco Systems Inc 1994 1-10 Bridging CHAPTER

Transparent Bridging

Cisco Systems Inc 1994 Transparent Bridging 2-1 Objectives

Upon compleflon of thHs moduHe you wUh be abbe to perform the foflowing tasks

Describe the basic functions of transparent bridging

Enable and configure transparent bridging on the Cisco router

Monitor transparent bridging operation in the router

2-2 Bridging Cisco Systems lnc 1994 Transparent Brdgng

EOE1

Three major funcflons

Learning

Forwarding/filtering frames

Loop avoidance

Cisco Systems Inc 1994 Transparent Bridging 2-3 Learning

E0 0260.8c01.llll

E0 0260.8c01.2222

______El 0260 8c01 3333 El 0260.8c01 .4444 0260.8c01 .1111 0260.8c01 .4444

0260.8c01 .3333 0260.8c01 .2222

Source MAC addresses are assocated wth ports

2-4 Bridging Cisco Systems Inc 1994 Forwarding

EO 0260.8c01.llll

EG 0260.8c01 .2222 O26O.8cO1.3333

El 0260.8c01 .4444 0260.8c01 .1111 0260.8c01 .4444

0260.8c01 .2222 0260.8c01 .3333

Traffic propagated to specffic destnaflons

Cisco Systems Inc 1994 Transparent Bridging 2-5 FUterng

EO O26O8cOl.llll

EO 0260.8c01 .2222

El 0260.8c01 .3333

El 0260.8c01 .4444 0260.8cOl .1111 0260.8c01 .4444

0260.8c01 .2222 0260.8c01 .3333

Congeston contro through network knowHedge

This does not refer to filtering as it is used in the sense of an access list Here filtering describes the normal of which operation transparent bridge does not forward packets unnecessarily

2-6 Bridging Cisco Systems inc 1994 Topoogcal Loops 11t

if ii

Brdged network can have mutipHe paths

Topological loops can result in broadcast storms

Cisco Systems Inc 1994 Transparent Bridging 2-7 Loop Avoidance

Spannng tree aDgorthms düsabe nterfaces

Transparent spanning tree protocols

DEC

IEEE 802.1D

The protocol elects root bridge

Each bridge selects the lowest cost path to the root bridge

Interfaces with alternate paths will block traffic to prevent loops

1994 2-8 Bridging Cisco Systems Inc Transparent Configuraflon Tasks

GobaH configuraton

Select spanning-tree protocol

Create bridge group

nterface configuraton

Assign to spanning-tree group

Define filters

Cisco Systems Inc 1994 Transparent Bridging 2-9 Transparent Configuration

Router config

bridge group-number protocol protocol4ype

SeHects the spanning tree protocoH

Router config-if

bridge-group groupnumber

Assigns an interface to brdge group

bridge protocol ieee mt

bridge-group intel bridge-group mt bridge-group

for The bridge protocol command defines specific spanning tree algorithm bridge group

bridge protocol field descriptions

decimal number from 1-9 group-numberidentifies particular set of bridged interfaces

Sometimes loosely referred to as bridge number

and are used for protocol-typeeither DEC IEEE or IBM Only DEC IEEE Transparent section bridging The IBM option will be discussed in the Source-Route Bridge

The bridge-group command assigns an interface to particular bridge group

bridge-group field descriptions

group-numbera decimal number from 1-9

will forward traffic Interfaces not participating in bridge group not bridged

Inc 1994 2-10 Bridging Cisco Systems Transparent Configuration cont

Router config

bridge group priority number

AssUgns prorty to the brdge

Router config-if

bridge-group group path-cost cost

Cost to use the outgong nterface

The bridge priority command assigns specific priority to the bridge assisting in the spanning tree

root definition The lower the priority the more likely the bridge will be selected as the root

bridge priority field descriptions

groupa number from 1-9

numberassigns the priority level value is 0-255 Default value is 128

The bridge-group path-cost command is used to assign path cost to particular interface to be

used in the spanning tree algorithm Default is 1000 Mbps/data rate of attached LAN

bridge-group path-cost field descriptions

groupnumber from 1-9

costnumber from 0-65535

The DEC and IEEE spanning tree protocols have different values

Cisco Systems Inc 1994 Transparent Bridging 2-11 Transparent Configuration Exampe

Cisco

bridge protocol dec

bridge priority 100 bridge protocol dec

bridge priority interface ethernet

bridge-group interface ethernet bridge-group path-cost 10 bridge-group interface ethernet interface ethernet bridge-group bridge-group bridge-group path-cost 10

Defaultit path cost for Ethernet is 100

Which router will become the root

Where will blocking occur

2-12 Bridging Cisco Systems Inc 1994 Encapsulated Bridging

another Encapsulated bridging carries Ethernet frames from one router to

frames Over WAN link bridged frames are encapsulated in standard WAN protocol

Encapsulated bridging is supported across FDDI links

Cisco Systems Inc 1994 Transparent Bridging 2-13 Encapsulated Bridging Configuraflon Example

Cisco Cisco

bridge protocol dec bridge protocol dec

interface ethernet interface ethernet

bridge-group bridge-group interface interface

bridge-group bridge-group

2-14 Bridging Cisco Systems Inc 1994 Controlling Bridge Access

Router config

access-list access-list-number permit deny source source-mask destination destination-mask byte-offset-in-packet size operator operand

Defines entry brdge traffic fiHter

Router config-if

bridge-group group input output-type-Iist access-list-number

Assgns an nput/output fflter to an nterface

The access-list command is used to establish bridge traffic filter

access-list field descriptions

The access-list-numberinteger that identifies the type of access list

standard access-list 700 through 799

extended access-list 1100 through 1199

type-code access-list 200 through 299

The type-code access-list varies from the example above in that the source address and source mask are

replaced by type-code and wild-mask

permitallows connection when packet matches an access condition

denydisallows connection when packet matches an access condition

sourceMAC Ethernet address in the fonn xxxxxxxx.xxxx

source-maskmask of MAC Ethernet source address bits to be ignored The router uses the source and

source-mask arguments to match the source address of packet

destinationMAC Ethernet value used for matching the destination address of packet

in the list in decimal byte-offset-in-packet range of values that must be satisfied access Specified or

in hexadecimal format in the form Oxnn The offset is the number of bytes from the destination address

The number of need to offset fiom the field it is not an offset from the start of the packet bytes you

destination address varies depending on the media encapsulation type you are using

be from size range of values that must be satisfied in the access list Must an integer through

operatora logical operator lt gt eq neq masked operand compares arbitrary bytes within the packet The value to be compared to or against

bridge-group type-list command links the selected access list to an interface The access list may be applied

as either an input or output list

Cisco Systems Inc 1994 Transparent Bridging 2-15 Bridge Fflter Exampe

bridge protocol dec

accesslist 201 permit 0x6004 Ox0000 access-list 201 deny 0x0000 OxFFFF

interface ethernet

bridge-group

bridge-group input-type-list 201 interface ethernet

bridge-group

bridge-group input-type-list 201

Bridge offly LAT

2-16 Bridging Cisco Systems Inc 1994 Montorng Transparent Bridging

Router show bridge

Total of 300 station blocks 295 free BG Hash Address Action Interface Age RX count TX count 00/0 FFFF.FFFF.FFFF discard 09/0 0000.OCOO.0009 forward EthernetO 49/0 0000.OCOO.4009 forward EthernetO CA/U AAOO.0400.O6CC forward EthernetO 25

Router

The show bridge command displays

Total of 300 station blockstotal number of forwarding database elements in the system The memory to hold bridge entries is allocated in blocks of memory sufficient to hold 300 individual entries When the number of free entries falls below 25 another block of memory sufficient to hold

another 300 entries is allocated Therefore the size of the bridge forwarding database is limited to the amount of free memory in the router

295 freenumber in the free list of forwarding database elements in the system The total

number of forwarding elements is expanded dynamically as needed

BGbridging group to which the address belongs

Hashhash key/relative position in the keyed list

Addresscanonical Ethernet ordered MAC address

Actionaction to be taken when that address is looked up choices are to discard or forward the datagram

Interfaceinterface if any on which that address was seen

Agenumber of minutes since frame was received from or sent to that address The letter

indicates permanent entry The letter indicates the system as recorded by the router On the

modular systems this is typically the broadcast address and the routefs own hardware address on the IGS this field will also include certain multicast addresses

RX countnumber of frames received from that address

TX countnumber of frames forwarded to that address

Cisco Systems Inc 1994 Transparent Bridging 2-17 Monitoring Transparent Bridging cont

Router show span Bridge Group is executing the IEEE compatible spaxining tree protocol lEE bridge domains are not used for this bridge group Bridge Identifier has priority 32768 address 0000.OcOO.ab4O Configured hello time max age 20 forward delay 15 We are the root of the spanning tree Acquisition of new addresses is enabled Forwarding of multicast source addresses is disabled LAT service filtering is disabled Topology change flag not set detected flag not set Times hold topology change 30 notification 30 hello max age 20 forward delay 15 Timers hello topology change notification Port Ethernet2 bridge group forwarding Path cost 100 priority Designated root has priority 32768 address 0000.OcOO.ab4O Designated bridge has priority 32768 address 0000.OcOO.ab4O Designated port is path cost Timers message age forward delay hold LAT compression is not set Input LAT service deny group code list is not set Input LAT service permit group code list is not set Output LAT service deny group code list is not set Output LAT service permit group code list is not set

of the The first line of output indicates which type spanning tree protocol IEEE or DEC bridge

group is executing

The next three lines show the current operating parameters of the spanning tree

the tree The remaining lines display related information that is useful when examining spanning

parameters

Port 9port number associated with the interface

Ethernet2interfaces on which Translational Bridging has been configured

to which the interface has been of bridge group 1bridge group assigned

is forwardingstate of the interface Other possible values include Down Listening Learning and Blocking

Path Cost 100path cost associated with this interface

priority 0port priority

1994 2-18 Bridging Cisco Systems Inc Summary

Transparent Brdgäng Funcflons

Learning

Forwarding

Loop Avoidance

Monitor transparent bridging operation in the router

Configuraflon

Select loop avoidance protocol

Create bridge group

Assign interfaces to bridge group

Cisco Systems Inc 1994 Transparent Bridging 2-19 22O Bridging Cisco Systems Inc 1994 CHAPTER

Source Route Bridging

Cisco 1994 Systems Inc Source Route Bridging 3-1 Objectives

Upon compHeton of ths moduHe you wUH be abHe to perform the foUowng tasks

Describe the basic functions of

sourceroute bridging

Enable and configure sourceroute bridging on the Cisco router

Monitor sourceroute bridging operation in the router

3-2 Bridging Cisco Systems Inc 1994 SourceRoute Bridging

RF RHF

500 500

501 505

502 502

Source chooses path to destnaflon

Explorer The method of one end host finding another end host

Three types

Local Ring Explorer

All Rings Explorer

Spanning Tree Explorer

The destination host replies to all explorers received

The source host uses the Routing Information Field RIF contained in the reply to learn and select

route through the network

Host transmits local ring explorer looking for Host on the local ring If this fails Host transmits an all-paths explorer which is copied by every bridge to adjacent rings

Inside of the explorer is the RIF which contains map of the path taken by this explorer packet

Host changes the direction bit in the Routing Control field of the R1F sending the packet back

exactly the way that it arrived Host receives maps identifying alternate routes to Host Host

gets to select the path it will use The source gets to choose the route hence source-route bridging

The path to the destination uses combination of token rings and source route bridges Inside the

data frame the RIF lists each bridge and ring that must be negotiated

IBM Token Ring specifies maximum of rings and bridges

802.5 Token Ring specifies maximum of 14 rings and 13 bridges

Cisco Systems Inc 1994 Source Route Bridging 3-3 Roufing nformaflon Fid

RF RC RD RD RD

Routing Control _____

___ Type Length Largest Direction Routing Descriptor

000 Specific route 100 All rings all routes 110 Spanning route IIHHflIHHH Ring Number Bridge Number

Contans contro and path nformaflon

Routing Information Field RIF

Can be to 18 bytes in size

Composed of the RC field and multiple RD fields

Routing Control Field RC

Type3 bits

000 specific route

100 all rings all routes

110 all rings spanning routes

Length5 bits

length of RIF measured in bytes

Directionwhich RIF way to interpret

Largest Framecode indicating largest frame accepted on route to the destination

Routing Descriptor RD

Ring Numberunique ring number within the network

Bridge Numberunique bridge number connecting two rings

34 Bridging Cisco Systems Inc 1994 SRB Configuration Tasks

MuNtiport Bridge

GHoba configuratäon

Define ring group

nterface configuratHon

Assign to ring group

Define type of explorer packets

Set up filters

Cisco Systems Inc 1994 Source Route Bridging 35 SRB Configuraflon

Router config-if

source-bridge active local-ring bridge-number target-ring

Specfies Hoca brdge connecflon

Router config

bridge group protocol ibm

Enabfles the automafic spannüng4ree protocoll

Router config-if

ource-bridge spanning group

Acflvates automafic spannng for an nterface

The source-bridge command is used to specify the ring and bridge number to which this interface

is attached

source-bridge field descriptions

local ringnumber of this interfaces ring

bridge-numbernumber between and 15 that uniquely identifies the bridge connecting the

two rings

target ringnumber of the target ring

bridge group protocol ibm

This command enables the dynamic spanning tree algorithm for bridging

and that identifies all interfaces that in the groupnumber between uniquely participates

automatic spanning algorithm

source-bridge spanning group

Command which activates the spanning algorithm for an interface

groupnumber between and that uniquely identifies all interfaces which will be

3-6 Bridging Cisco Systems Inc 1994 Manual Spanning Tree Support

Router config-if

source-bridge spanning

no source-bridge spanning

ManuaPHy enabHes or dflsabHes the passHng of spanning or sngHe route expHorers

The source-bridge spanning command is used to specify that this interface is capable of forwarding

spanning explorer If spanning tree is not automatically run the tree must be manually

configured on each forwarding interface

Cisco Systems Inc 1994 Source Route Bridging 3-7 SRB Basc Configuraflon Exampe

Two Ioca rings

Brdge1

interface tokenring sourcebridge active 500 501 sourcebridge spanning

interface token ring sourcebridge active 501 500 sourcebridge spanning

bridge protocol ibm

3-8 Bridging Cisco Systems Inc 1994 SRB Compex Configuration

Token Token Virtual Ring Ring Ring 501 -e50 10 \_

Ii .11

Token\ Ring

502

Router config

Creates vürtuaD ring

The source-ring ring-group command is used to build software-generated virtual ring inside the This router virtual ring is required when more than two Token Ring interfaces are connected to the router

source-ring ring-group field descriptions

ring-groupnumber of the virtual ring it replaces the target ring number

Cisco Systems Inc 1994 Source Route Bridging 3-9 SRB ComplexConfiguration Example

Token Token

Brdge

source-bridge ring-group 10

interface tokenring source-bridge active 500 110 source-bridge spanning

interface tokenring source-bridge active 501 110 source-bridge spanning

interface tokenring source-bridge active 502 110 source-bridge spanning

bridge protocol ibm

3-10 Bridging Cisco Systems Inc 1994 Proxy Exporer

Router config-if

sourcebridge proxyexpIorer

EnabOes the interface to respond to expHorer packets

The sourcebrkIge proxyexp1orer command enables the router to respond to explorer packets The

contents of the RJF cache are used to describe the path to the destination end host

Cisco Systems Inc 1994 Source Route Bridging 3-11 multiring Command

Router config-if

f1itiring Iotherlkeyword

Enabes the coD Decflon and use of RDF Dnformaflon

The multiring field description

allenables multiring for all frames

routed frame that is the listed otherenables multiring for any not among supported protocols under keyword below

keywordspecifies routed protocol that will have RIF information inserted in its frame

Options include apollo appletalk clns decnet 1F ipx vines xns

order In the example above two routed domains are separated by source-route bridged domain In

for the routed frames to traverse the source-route bridged network the routed frames must have RIF

fields inserted

The multiring command enables these routed frames to pass through the SRB bridge

1994 3-12 Bridging Cisco Systems Inc MutIring Configuration Exampe

interface to

multiring ip ip address 13t108.183.37 2552552550

Cisco Systems Inc 1994 Source Route Bridging 3-13 Monitoring SRB

Router show source-bridge

Local Interfaces max receive transmit sm bn tm hp cntbytes cntbytes drops

TRO 10 391002 2362923

Rings bn rn local ma 4000.3080.844b TokenRingO fwd 18 bn rn remote ma 4000.3080.8473 TCP 150.136.93.93 fwd 36

Explorers input output spanning all-rings total spanning all-rings total TRO

Router

Local Interfaces description of local interfaces

maxmaximum routing descriptor length

receive Packetsbytes received on interface for source-route bridging

transmit Packets bytes transmitted on interface for source-route bridging

smring number of this Token Ring

hobridge number of this router for this ring

tmgroup in which the interface is configured the target ring number or virtual ring group

rring group is assigned An asterisk in this field indicates that ring group has been assigned for this

interface

pinterface can respond with proxy explorers An asterisk in this field indicates that the interface can

respond to proxy explorers

sspanning-tree explorers enabled on the interface An asterisk indicates that this interface will forward

spanning-tree explorers

ninterface has NetBIOS name caching enabled An asterisk in this field indicates that the interface has

NetBIOS name caching enabled

hpindicates hops

Ringsdescribes the ring groups Information displayed includes the bridge groups ring groups whether of the group is local or remote the MAC address the network address or interface type and the number

packets forwarded

Explorersthis section describes the explorer packets that the router has transmitted and received

TROinterface on which explorers were received spanningspanning-tree explorers

all-ringsall-rings explored totalsummation of spanning and all-rings

1994 3-14 Bridging Cisco Systems Inc Monitoring SRB cont

Router show rif

Codes interface static remote Hardware Addr How Idle mm Routing Information Field 5C02.000l.4322 rg5 0630.0053.OOBO 5A00.0000.2333 TRO 08B0.OlOl.220l.OFFO 5B01.0000.4444 0000.1403.4800 TR1 0000.2805.4C00 TRO 0000.2807.4C00 TR1 0000.28A8.4800 TRO

0077.2201.0001 rg5 10 0830.0052.2201.OFFO

Router

The show rif command displays

Howdescribes how the RIF has been learned Possible values include ring group rg or interface TR

Idle minindicates how long in minutes since the last response was received directly from

this node

Routing Information Fieldlists the RIF

Cisco Systems Inc 1994 Source Route Bridging 3-15 Summary

Source Route Brädgng uses speca exporer packets to cflscover routng nformaflon the network and return to the host system

Configurng SRB requires configuraflon between the source ring cflrecthy connected to the router and target ring

target ring can ether be another Token Rng or vrtuaH rng cafled ring group

ExpHorer traffic can be effected by usng spanning options

316 Bridging Cisco Systems Inc 1994 CHAPTER

MixedMedia Bridging

Cisco Systems Inc 1994 Mixed-Media Bridging 4-1 Objectives

Upon compeflon of this moduHe you wUH be abHe to perform the foHowng tasks

Describe mixed-media bridging options

Explain typical applications for various types of bridging

Configure Source Route Transparent bridging

Configure Source Route Translational bridging

4-2 Bridging Cisco Systems Inc 1994 MxedMeda Bridging

Cisco 1994 Systems Inc Mixed-Media Bridging 4-3 MixedMedia Bridging

What Bridge Type This

44 Bridging Cisco Systems Inc 1994 RFs Are Appflcation Dependant

What Bridge Type This

Ic5n RW

No RIF

Cisco Systems nc 1994 Mixed-Media Bridging 45 MixedMedia Sampe

No ROF

4-6 Bridging Cisco Systems Inc 1994 MxedMedia Bridging

What Bridge Type This

Cisco Systems nc 1994 Mixed-Media Bridging 4-7 MxedMedia Bridging

What Bridge Type Hs This

J9r RF

RIF

Appflcaflon uses RMFs

4-8 Bridging Cisco Systems Inc 1994 MixedMedia Bridging

What Bridge Type This

NoRIF

No RIF

Appflcaflon does not use RFs

MTU the same

Cisco Systems Inc 1994 Mixed-Media Bridging 4-9 MixedMedia Bridging

Under What Conditons Wifi This Work

No RFs aflowed MTU 1500

Bt Ordering

Csco reverses MAC address

Issues concerning different media types

Bit ordering on Ethernet and Token Ring is different

Ethernet uses LSB Least Significant Bit First

Token Ring uses MSB Most Significant Bit First

Token Ring supports one frame format LLC while Ethernet supports two frame formats LLC and EthernetAdditionally both support SNAP

SNAP vendor code of OO-OO-F8 on Ethernet-to-Token Ring transmissions allows bridges to

recognize encapsulation type

Token Ring frames must be 64 bytes and 1518 bytes to match the capacity of Ethernet

Token Ring frames may contain RIF field Ethernet has no equivalent

In source-route bridging the end systems are aware of the existence of the bridge In transparent

bridging the end systems do not know that the bridge exists

Caution Mixing routing and translational bridging is normally difficult in single router

4-10 Bridging Cisco Systems Inc 1994 MixedMecIia Bridging

What Bridge Type This

MTU RF

Bt Orderng

EncapsuHaflon

Cisco Systems Inc 1994 Mixed-Media Bridging 4-11 Not sure about RFs

Do both TB and SRB

CaVed SRT Source Route Transparent

Source-Route Transparent Bridging SRT

Defines source-route bridging as an optional protocol on top of transparent bridging

Handles both and the source-route transparent at same time one packet per transfer

In general Token Ring to Ethernet communication is not provided by SRT the two domains are

kept separate with some exceptions

412 Bridging Cisco Systems Inc 1994 Cisco as SRT Bridge

Source Route Transparent Bridging Bridging Module Module

Csco examnes Token Rng frame for RF fieHd

If RIF is present then pass the frame to the SRB software module

If no RIF is present then pass the frame to the TB software module

Cisco SRT can use either IEEE or DEC spanning tree algorithms

Interoperability with non-Cisco SRT bridges requires the IEEE spanning tree algorithm be

configured in the router

Cisco Systems Inc 1994 Mixed-Media Bridging 4-13 SRT Configuraflon Tasks

Transparent Configuraflon

Define the transparent bridge group

Select spanning protocol

Assign interfaces to bridge group

Source Route Configuraflon

For multiport create virtual ring

Activate ringbridgering connection

Define SRB spanning bridge group

Select interface spanning option

Define OUl for Ethernetll frames

The used has bridge-group command as above several meanings The meaning is determined by

the type of interface to which it is applied

Ethernet 0use transparent bridging

Token Ring 0use source-route bridging

Serial 0use encapsulated bridging

The for commands configuring source-route transparent bridging are identical to those for

configuring transparent bridging

4-14 Bridging Cisco Systems Inc 1994 SRT Configuraflon

Transparent Commands

Router config

bridge groupnumber protocol protoco4ype

SeHects the spanning tree protoco

Router config-if

brdgegroup groupnumber

Assgns an nterface to brdge group

Brdgegroup appfled to Token Ring interfaces for SRT

Cisco Systems Inc 1994 Mixed-Media Bridging 4-15 SRT Configuraflon cont0

Source Route Commands

Router config

urcebridge ringgroup ringgroup

Defines or removes rng group

Router config-if

active Iocaring bridgenumber targetring

Specffies vocal bridge connecton

416 Bridging Cisco Systems Inc 1994 SRT Configuration cont

Router config

bridge group protocol ibm

EnabHes the automafic spannng4ree protoco

Router config-if

source-bridge spanning group

Acflvates automatc spannng for an ünterface

Router config-if

source-bridge spanning

Manually enabes spannng explorer support

These commands are identical to those discussed in Source Route Bridging

Cisco Systems Inc 1994 Mixed-Media Bridging 4-17 SRT Configuraflon Exampe 1A

bridge protocol ieee

source-bridge ring-group 10 bridge protocol ibm interface ethernet

bridge-group interface ethernet

bridge-group interface tokenring bridge-group Transparent source-bridge active 500 110 source-bridge spanning

interface tokenring bridge-group

source-bridge active 501 110 source-bridge spanning

4-18 Bridging Cisco Systems Inc 1994 Can SRT Sove This Probem

TBandSRB must task

Appflcatüon on uses RFs

SRITLB Source Route TransDaflona Brdgng

Cisco Systems Inc 1994 Mixed-Media Bridging 419 Tranaflona Brdging

RF Stnpped

RIF Added

Handles MTU

Handles bt ordering

AA 55

1010 1010 0101 0101

Source-Route Translational Bridging SRJTLB

Allows the combining of existing source-route bridged and transparent bridged networks

Brings the Token Ring and Ethernet domains together

Enables device on Token Ring to communicate with device on Ethernet

When bridging from the SRB domain to the transparent bridging domain the RIFs are removed

the To the source-route bridged domain transparently bridged domain appears as pseudo ring another SRB domain

Spanning tree packets are not sent through the other pseudo SRB domain

When bridging from the transparent domain to the SRB domain the packet is checked to determine

if it is multicast or unicast

If it is multicast the packet is sent as spanning tree explorer

If it is unicast the RIF is looked up in the RIF cache If no entry is found in the RIF cache then the

packet is sent as spanning tree explorer

4-20 Bridging Cisco Systems Inc 1994 SRITLB Configuraflon Tasks

Configure SRB and TB for your envfronment

Goba configuration

Set up translational bridge

Define pseudo ring

Define bridge number

Cisco Systems mc 1994 Mixed-Media Bridging 4-21 SRB and Transparent Sampe

To SRB

To Transparent Bridging

4-22 Bridging Cisco Systems Inc 1994 SR/TLB Configuraflon

Router config

sourcebrdge transparent ringgroup pseudoring bridgenumber tbgroup

Enabes brdgng between the transparent brklge configuraflon and the sourceroute brdge configuraflon

Before using the source-bridge transparent command source-route bridging and transparent

bridging must be configured

The source-bridge transparent command is used to create two new fully compatible environments for the domain one SRB and one for the transparent domain

source-bridge transparent field descriptions

rgring group SRB virtual ring The virtual ring-group that was created by the

source-bridge ring-group command

prpseudo ring Assigns ring number for the transparent domain The number must

be unique SRB domain

bnbridge number the SRB number assigned to the router

tbgtransparent bridge group number The number assigned to the virtual Ethernet

that contains the SRB domain

Cisco Systems Inc 1994 Mixed-Media Bridging 4-23 SRITLB Configuraflon Exampe

bridge protocol ieee

source-bridge ring-group 10

bridge protocol ibm source-bridge transparent 10 13 interface ethernet bridge-group interface ethernet

bridge-group interface tokenring bridge-group source-bridge active 500 110 rU source-bridge spanning interface tokenring Transparent bridge-group Source Route source-bridge active 501 110 source-bridge spanning SRITLB

4-24 Bridging Cisco Systems Inc 1994 Ethernet Transit

Router config-if

ethernet4ransit-oui 9Ocompatible standard cisco

Selects Ethernet type II Organizational Unique Identifier OUI encapsulation code

Router config-if

sourcebridge enable 80D5

Selects enhanced compatibility Ethernet encapsulation

If Ethernet is passing through the Token Ring backbone you can select the encapsulation type This

could be accomplished with Source Route Translational Bridging on both bridges but it would

double the translation overhead If the Ethernet is passing through and no host stations on the Token

Ring are connecting then Source Route Transparent bridging generates less overhead

The ethernet-transit-oui command makes it possible to change the Organizationally Unique

which is Identifier method for encapsulating Ethernet

The source-bridge enable-80D5 command is used for compatibility with IBM 8209 bridges which

use different method of encapsulation

Cisco Systems Inc 1994 Mixed-Media Bridging 4-25 Encapsulated Brdgng

Frame

Serial Frame

Frame

FDDI Frame

Duing

4-26 Bridging Cisco Systems Inc 1994 EncapsuNated Brdgng on FDD

fddi encapsulate

DHsabes transHaflona brdgng and enabHes encapsuHated brdging

The fddi encapsulate command disables translational bridging and allows to talk to

Some interfaces will not allow translational bridging It is supported on

Cisco 7000/7010

AGS with the C2CFCIT card

Cisco4000/4500

Cisco Systems Inc 1994 Mixed-Media Bridging 4-27 Encapsulated Bridging Configuration Example

Cisco Cisco

bridge protocol dec bridge protocol dec

interface ethernet interface ethernet

bridge-group bridge-group interface interface

bridge-group bridge-group

Using the spanning algorithm dec requires less overhead than IEEE

But you must have Cisco routers on both ends

4-28 Bridging Cisco Systems Inc 1994 How Do You Bridge to

Token JnToken

Tunneflng Remote Source Route Brdgng RSRB

Cisco Systems Inc 1994 Mixed-Media Bridging 4-29 Summary

Csco offers many features for mixed mecila brdgng

Source Route Transparent SRI

Source Route and Transparent coexisting

Source Route Translational SRITLB

Source Route and Transparent communicating

Encapsulated Bridging

Remote Source Route Bridging RSRB

Configuraflon choce depends on host appflcaflon charactersflcs

4-30 Bridging Cisco Systems Inc 1994 CHAPTER

Remote SourceRoute Bridging

Cisco Systems Inc 1994 Remote Source-Route Bridging 5-1 Objecflves

Upon compeUon of ths moduHe you waD be abOe to perform the followang tasks

Describe the basic functions of remote sourceroute

bridging

Explain the various types of remote sourceroute bridging

Enabe and configure remote sourceroute bridging on the Cisco router

5-2 Bridging Cisco Systems Inc 1994 RSRB Overvew

Token\ Hi fl9 \OV

De.encapsuI

Routed packet

Issues concerning remote source-route bridging RSRB

Encapsulates Token Ring frame inside an arbitrary media

Routes frames across arbitrary media

De-encapsulates Token Ring frame and places it on target ring

Cisco 1994 Systems Inc Remote Source-Route Bridging 5-3 RSRB Tunnefing

Virtual Ring

TCP/IP Network Token\ Token\

Ring Ring

Token Ring frames are tunned through TCP/flP or HDLC

The tunneD treated as vrtuaO Token Rng

5-4 Bridging Cisco Systems Inc 1994 RSRB Ring Groups

Token lg

S_ Virtual

Token Ring Token\

5-- Token

Token Token Ring Rin-//

RSRB tunns TCP/P DIIRECT treated as virtua Token Ring

Other routers are remote peers attached to the virtuaH Token Ring

Cisco Systems Inc 1994 Remote Source-Route Bridging 5-5 Types of RSRB Tunns

TCP and EncapsuUaflon

MuDflpDe paths are avaflabHe

TCP and IP encapsulation allows for arbitrary topologies There are no hop count limitations and

traffic is routable

Software overhead varies

TCP high overhead very reliable

IP medium overhead datagram service

IP encapsulation is sometimes referred to as Fast Sequenced Transport FST

56 Bridging Cisco Systems Inc 1994 Types of RSRB Tunns cont

Dkect Encapsuaton

Tok\ RInJ

SngHe path avaflabHe

Direct encapsulation restricts traffic to single topology There is single hop count limit and traffic

is not routable

Software overhead is minimal error checking is done at the hardware level

Cisco Systems Inc 1994 Remote Source-Route Bridging 5-7 RSRB Configuration Tasks

Direct Encapsulation

Token FDD TRegn

GHoba configuraflon

Define ring group

Identify remote peers

Onterface configuraton

Enable SRB

5-8 Bridging Cisco Systems Inc 1994 RSRB Configuraflon

Router config

source-bridge ring-group ring-group-number

Creates vrtuaH rng

Router config

source-bridge remote-peer ring-group fst ip-address

dentffies the address of peer statäon connected to the vfrtuaH ring

SeHects encapsuHaflon styHe

The is source-ring ring-group command used to build software-generated virtual ring inside the

router This virtual ring is required when more than two Token Ring interfaces are connected to the router

source-ring ring-group field descriptions

ring-groupnumber of the virtual ring it replaces the target ring number The source-bridge remote-peer command is used to establish peer relationship between routers

attached to virtual ring

source-bridge remote-peer field descriptions

ring-groupring group number This ring group number must match the number you have

with the The valid is 1-4095 specified source-bridge ring-group command range

tcpencapsulation style Reliable delivery with high software overhead

fstencapsulation style Datagram delivery with medium software overhead

address of the remote with which the will ip-address IP peer router communicate

Cisco 1994 Systems Inc Remote Source-Route Bridging 5-9 RSRB Configuration Sample

Cisco

CiscoA CiscoB

SO Netwo 138.100.5.1 138.100.6.1

Token

okeli Ring

the Example configuration commands are on following page

1994 5-10 Bridging Cisco Systems Inc RSRB Configuraflon Example

Cisco sourcebridge ringgroup ABC sourcebridge remotepeer tcp 138.100.6.1 sourcebridge remotepeer tcp 138.100.5.1 sourcebridge remote.peer tcp 138.100.7.1

Cisco interface tokenring ip address 138.100.5.1 255.255.255.0 sourcebridge 501

Cisco

Cisco diJ

Cisco 1994 Systems Inc Remote SourceRoute Bridging 51 Summary

RSRB tunneUng of SRB frames across an coud

There are severah afternafives for encapsulaflon

TCP

Reliable transport layers of encapsulation overhead

FST

TopologicaHy dependent but faster

Direct

Fastest but not routable one hop only

512 Bridging Cisco Systems Inc 1994 Cerperate Headquarters

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