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RIPv2 / routing domain

                   hello

i found that there is a field in RIPv2 header that is : routing domain.

it seems to be like a process id (like vlan id) so that routers that do not have the same routing domain will not process RIPv2 packets.

1-am i right ?

2-how to change the value of this field?

thanks

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Hall of Fame Cisco Employee

Re: RIPv2 / routing domain

Hello,

I believe I now know more about the "routing domain".

RIPv2 was first codified in RFC 1388. This RFC indeed defined a Routing Domain field inside the RIP message header. The Routing Domain was defined as follows (RFC 1388 Section 3.2):

   The Routing Domain (RD) number is the number of the routing process
   to which this update belongs.  This field is used to associate the
   routing update to a specific routing process on the receiving router.
   The RD is needed to allow multiple, independent RIP "clouds" to co-
   exist on the same physical wire.  This gives administrators the
   ability to run multiple, possibly parallel, instances of RIP in order
   to implement simple policy.  This means that a router operating
   within one routing domain, or a set of routing domains, should ignore
   RIP packets which belong to another routing domain.  RD 0 is the
   default routing domain.

However, in the RFC 1721 "RIP Version 2 Protocol Analysis", Section 2 states:

   The significant change from RFC 1388 is the removal of the domain
   field.  There was no clear agreement as to how the field would be
   used, so it was determined to leave the field reserved for future
   expansion.

As a result, the updated RIPv2 RFCs, namely RFC 1723 and the current RFC 2453, removed the Routing Domain tag and instead treat the field as Must-Be-Zero, or unused. Your Wireshark obviously believes that the RFC 1388 RIPv2 is being run and tries to interpret an unused field in the RIPv2 header.

I have just now found out that this behavior in Wireshark can be configured: Choose Edit -> Preferences, then click on Protocols, find the RIP, and there you will see a checkbox saying "Display Routing Domain field". Uncheck it.

Best regards,

Peter

7 REPLIES 7
Hall of Fame Cisco Employee

Re: RIPv2 / routing domain

Hi,

This is an interesting information. Where did you learn about such field? I have consulted the RFC 2453 and Sections 3.6 and 4 state only these fields in an RIPv2 message: Command, Version, Must-Be-Zero, and a RIP entry that consists of AFI, Route Tag, IP Address, Subnet Mask, Network, Metric.

Best regards,
Peter

Sent from Cisco Technical Support iPad App

Contributor

Re: RIPv2 / routing domain

i just captured a RIPv2 packet using wireshark and GNS3/Cisco3600 router.

but i can't find a command under roter rip to set its value

Hall of Fame Cisco Employee

Re: RIPv2 / routing domain

Hello,

Can you post the packet you have captured? I have done the same and I do not see anything related to a "routing domain" in my capture. Please observe the attached PCAP file of RIPv2 packets and a screenshot of my Wireshark.

Best regards,

Peter

Contributor

Re: RIPv2 / routing domain

Hall of Fame Cisco Employee

Re: RIPv2 / routing domain

Hello,

Alright What Wireshark version are you using? I am running 1.8.2.

Best regards,

Peter

Hall of Fame Cisco Employee

Re: RIPv2 / routing domain

Hello,

I believe I now know more about the "routing domain".

RIPv2 was first codified in RFC 1388. This RFC indeed defined a Routing Domain field inside the RIP message header. The Routing Domain was defined as follows (RFC 1388 Section 3.2):

   The Routing Domain (RD) number is the number of the routing process
   to which this update belongs.  This field is used to associate the
   routing update to a specific routing process on the receiving router.
   The RD is needed to allow multiple, independent RIP "clouds" to co-
   exist on the same physical wire.  This gives administrators the
   ability to run multiple, possibly parallel, instances of RIP in order
   to implement simple policy.  This means that a router operating
   within one routing domain, or a set of routing domains, should ignore
   RIP packets which belong to another routing domain.  RD 0 is the
   default routing domain.

However, in the RFC 1721 "RIP Version 2 Protocol Analysis", Section 2 states:

   The significant change from RFC 1388 is the removal of the domain
   field.  There was no clear agreement as to how the field would be
   used, so it was determined to leave the field reserved for future
   expansion.

As a result, the updated RIPv2 RFCs, namely RFC 1723 and the current RFC 2453, removed the Routing Domain tag and instead treat the field as Must-Be-Zero, or unused. Your Wireshark obviously believes that the RFC 1388 RIPv2 is being run and tries to interpret an unused field in the RIPv2 header.

I have just now found out that this behavior in Wireshark can be configured: Choose Edit -> Preferences, then click on Protocols, find the RIP, and there you will see a checkbox saying "Display Routing Domain field". Uncheck it.

Best regards,

Peter

Contributor

Re: RIPv2 / routing domain

thanks Mr  Peter for your help

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