EBGP and multihops

Hello,

After labing a bit with EBGP neighbors using loopback interfaces I have some
observations. Perhaps someone can clarify if I am correct:

R1-------------------R2
AS 100 AS 200
L0: 1.1.1.1 L0: 2.2.2.2

The task is to establish neighborships between R1 and R2 using L0
interfaces.

I think that three methods are possible.
Following examples show R1 configurations, R2 has reverse configuration:
 
Method 1:
Router bgp 100
 neighbor 2.2.2.2 update-source Loopback0
 neighbor 2.2.2.2 ebgp-multihop (+ optional hop count, default is 255)

Method 2:
Router bgp 100
 neighbor 2.2.2.2 update-source Loopback0
 neighbor 2.2.2.2 ttl-security hops (+ mandatory hop count)

Method 3:
Router bgp 100
 neighbor 2.2.2.2 update-source Loopback0
 neighbor 2.2.2.2 disable connected check

My understanding is that all methods will play with TTL of packets sent from
one neighbor to another thus allowing packets to reach defined neighbor. In
that sense method 1 and 2 are identical as TTL can be defined.
Method 3 is a bit different as it will set TTL to 255 and there is no way to
change it.

Am I right ?

Thanks,

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Received on Fri Aug 20 2010 - 00:24:59 ART