RE: Update-source in EBGP

From: Jason Sinclair (sinclairj@xxxxxxxxxxxxxxx)
Date: Mon Mar 11 2002 - 01:01:15 GMT-3


   
Bill,

Generally you are correct regarding the TTL, however consider when you are
multihomed and physically lose connectivity to your peer. If the TTL is too
high, there is a real possibility that your BGP tcp connection will
re-establish the long way round through your other peer. This makes life
interesting!!

Cheers,

Jason Sinclair
Manager, Network Support Group
POWERTEL
Ground Level, 55 Clarence Street,
SYDNEY NSW 2000
AUSTRALIA
office: + 61 2 8264 3820
mobile: + 61 416 105 858
* sinclairj@powertel.com.au

                -----Original Message-----
                From: Bill Hill [mailto:bhill@sgdata.com]
                Sent: Monday, 11 March 2002 12:29
                To: RSiddappa@NECBNS.com; tsabry@houston.sns.slb.com;
ccielab@groupstudy.com
                Subject: RE: Update-source in EBGP

                the "ttl" is optional, if you do not specify, it will
default to 255 and will just increase the possible diameter of your network,
ugly maybe but shouldn't hurt anything. (I am sure there are some security
guys out there freaking out right about now!)

                -----Original Message-----
                From: RSiddappa@NECBNS.com [mailto:RSiddappa@NECBNS.com]
                Sent: Sunday, March 10, 2002 9:23 PM
                To: Bill Hill; tsabry@houston.sns.slb.com;
ccielab@groupstudy.com
                Subject: RE: Update-source in EBGP

                What will happen If I do nto specify the hops ?

                I have seen it taking 255. What effect will it have ?

                R.

                -----Original Message-----
                From: Bill Hill [mailto:bhill@sgdata.com]
                Sent: Sunday, March 10, 2002 8:02 PM
                To: Tarek Sabry; ccielab@groupstudy.com
                Subject: RE: Update-source in EBGP

                You can have any IP from one router peer to any other IP of
another router
                as long as there is a route between the two.

                You only require ebgp-multihop if the 2 peer routers IP
addresses are not
                directly connected using the same linke, ie: 2 physical
endpoints. If so,
                you count the number of layer-3 hops between the 2 endpoints
and use that as
                the parameter. And just to state the obvious, ebgp-mutihop
is ony used when
                you connect different AS's.... ie EBGP, not IBGP.

                HTH
                -Bill

                -----Original Message-----
                From: Tarek Sabry [mailto:tsabry@houston.sns.slb.com]
                Sent: Sunday, March 10, 2002 8:37 PM
                To: ccielab@groupstudy.com
                Subject: Update-source in EBGP

                Quick question:

                Do I have to have symmetrical configs on both sides? Can I
have one loopback
                on one AS try to peer with th serial on the other AS?

                Also do I have to have "ebgp-multihop" whenever I use
"update-source lo0"?

                Thanks
                Tarek
        



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