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BGP EBGP hops

kswonnell
Beginner
Beginner

Max EBGP hops is 255.

In a confederation AS, do the member AS numbers count as part of the AS path i.e. does the 255 max include confederation ASs ?

6 REPLIES 6

donewald
Frequent Contributor
Frequent Contributor

EBGP hops are counted by router hops, not AS hops. So, yes confederation AS members would be counted, as would any router.

Hope this helps,

Don

Let me rephrase the question:

The AS_Path attribute is up to 255 AS entries in length. If the AS path contains confederation AS numbers, are they counted as part of the 255 ?

Yup, they are included when checking for the maximum lenght. Keep in mind that when the prefix leaves the confed, the confereration info is stripped. But yes, if you got a prefix with an AS path lenght of 253 and then the prefix transited 2 confederations, you would have to make the prefix as invalid.

Good answer Warren; thanks

angelsoft
Beginner
Beginner

From the IOS, IP routing command index, located at:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/ip_r/iprprt2/1rdbgp.htm#xtocid46

neighbor ebgp-multihop

To accept and attempt Border Gateway Protocol (BGP) connections to external peers residing on networks that are not directly connected, use the neighbor ebgp-multihop router configuration command. To return to the default, use the no form of this command.

neighbor {ip-address | peer-group-name} ebgp-multihop [ttl]

no neighbor {ip-address | peer-group-name} ebgp-multihop

Syntax Description

ip-address

IP address of the BGP-speaking neighbor.

peer-group-name

Name of a BGP peer group.

ttl

(Optional) Time-to-live in the range 1 to 255 hops.

-----

This means that the hops are actually the TTL of the IP packets.

If you don't know what TTL is, then you should be reading more TCP/IP

protocol suite books.

BR,

Zvezdelin

Thanks for the answer but you misunderstood my question. It wasn't about TTL or router hops, it was about ASs.

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