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EIGRP internal tag

1. Does anyone know in what IOS version EIGRP internal tag (0-255) support was added?

2. What happens if these tagged internal routes propagate through EIGRP hops that do not support EIGRP internal tag, is the tag retained?

Thanks

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EIGRP internal tag

I totally botched the ddts number (that's what happens when you do it from memory and you didn't do the work.)

The change went in via CSCdw22585 and was committed back in 2003.  It appears it initially went into 12.3T. 

As for whether it gets stripped, the internal tag took advantage of an unused 8 bit field in the packet (thus the limit to 255 values versus the 32 bit value of an external tag).  This field is created by each router as it sends the packet, therefore if it goes through a router running old enough code to not support the feature, the field would not be propagated.

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Re: EIGRP internal tag

Judging from this

http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094cb7.shtml#admintags

It's always been available

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EIGRP internal tag

Jeff, that's the external tag that we use during redistribution, I'm referring to the internal tag.

Bronze

Re: EIGRP internal tag

1. Does anyone know in what IOS version EIGRP internal tag (0-255) support was added?

I'll try to look it up tomorrow, but it came in as part of some route-map enhancements several years ago. CSCdy20855 or something like that.

2. What happens if these tagged internal routes propagate through EIGRP hops that do not support EIGRP internal tag, is the tag retained?

Nope. It will be removed.

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EIGRP internal tag

Interesting, yes, if you can point me to any documentation or enhancement ID, I would appreciate it!

I should probably test if it gets removed though, are you 100% sure? That's unfortunate I hope my routers in the path are running IOS new enough to support it then.

Bronze

EIGRP internal tag

I totally botched the ddts number (that's what happens when you do it from memory and you didn't do the work.)

The change went in via CSCdw22585 and was committed back in 2003.  It appears it initially went into 12.3T. 

As for whether it gets stripped, the internal tag took advantage of an unused 8 bit field in the packet (thus the limit to 255 values versus the 32 bit value of an external tag).  This field is created by each router as it sends the packet, therefore if it goes through a router running old enough code to not support the feature, the field would not be propagated.

EIGRP internal tag

12.3T? That's great, that's very old. Thanks for your help

New Member

Hello,I think that you are a

Hello,

I think that you are a little bit wrong.

-> here is an "show ip ei top" from 2900 with 15.2.4M6 and Internal TAG is greater than 255:

"

 10.126.254.251 (Tunnel22), from 10.126.254.251, Send flag is 0x0
      Composite metric is (10240/5120), route is Internal
      Vector metric:
        Minimum bandwidth is 100 Kbit
        Total delay is 400 microseconds
        Reliability is 255/255
        Load is 2/255
        Minimum MTU is 1472
        Hop count is 2
        Internal tag is 1000

"

-> here is the output from an 1841 running 15.1.4M8 and as you can see the Internal Tag is missing:

"

  10.126.254.251 (Tunnel22), from 10.126.254.251, Send flag is 0x0
      Composite metric is (10240/5120), route is Internal
      Vector metric:
        Minimum bandwidth is 100 Kbit
        Total delay is 400 microseconds
        Reliability is 255/255
        Load is 12/255
        Minimum MTU is 1472
        Hop count is 2
  10.126.254.252 (Tunnel22), from 10.126.254.252, Send flag is 0x0

"

 

Both 2900 & 1841 have an EIGRP adjacency with the same 10.126.254.251 which set the Internal TAG to 1000 via an route-map used for distribute-list. On the 2900 the Internal TAG is appearing, on the 1841 is not. I even tried to set the Internal TAG on input on 1900 (again with a route-map used for distribute-list) and it does not work.

And the DDTS mentioned by you says nothing about TAGs.

 

 

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