From: Jason Sinclair (sinclairj@xxxxxxxxxxxxxxx)
Date: Mon Mar 11 2002 - 02:02:43 GMT-3
Bill,
I guess that is right. However, on the point about the static route,
remember that will disappear when the int goes down. Now if you are learning
that route from another peer then you will connect that way. Try it in a lab
and you'll see what I am getting at. As to probability you are right I was
probably a bit generous there. I work in an ISP environment and have seen it
happen twice.
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 13:18
To: Jason Sinclair; RSiddappa@NECBNS.com;
tsabry@houston.sns.slb.com; ccielab@groupstudy.com
Subject: RE: Update-source in EBGP
Hmmm, I don't know about that.
If I am at a router, and have established a peer with an
EBGP neighbor, unless I run a routing protocol, I am going to have to create
a static route to that destination. In the same manner, the ISP will create
a static to get back to my loopback via that same link. In the event of a
failure of a link in a multi-homed organization, I'm not sure that I would
be advertising via that other router or via that other path as a route to my
original peer.
When doing EBGP via an ISP, they usually prefer to use the
directly connected IP address of the physical link.... unless you are using
multiple connections to the same ISP and do loopback peering. Along the
same lines, and correct me if I am wrong, they are not going to advertise or
use an additional path/route to your loopback or physical interface address.
I guess in some situations, and if the stars were in
alignment, it may be possible, but I would want to change what you said of
"high possibility" to remote possibility.
Is this correct? Did that make any sense? (It's late and I
have had a few glasses of wine. ;-) ) I don't work for an ISP but have seen
many multi-homed networks.
-Bill
-----Original Message-----
From: Jason Sinclair [mailto:sinclairj@powertel.com.au]
Sent: Sunday, March 10, 2002 11:01 PM
To: Bill Hill; RSiddappa@NECBNS.com;
tsabry@houston.sns.slb.com;
ccielab@groupstudy.com
Subject: RE: Update-source in EBGP
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
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 10:56:59 GMT-3