RE: Using Tunnels with iBGP

From: Edwards, Andrew M (andrew.m.edwards@boeing.com)
Date: Fri Aug 06 2004 - 13:18:55 GMT-3


You could also enable ip accounting on the tunnel interface, clear the
logs, and look at the logs for the accounting data...

andy

-----Original Message-----
From: ccie2be [mailto:ccie2be@nyc.rr.com]
Sent: Friday, August 06, 2004 9:03 AM
To: James
Cc: 'Brian McGahan'; 'Group Study'; samccie2004@yahoo.co.uk
Subject: Re: Using Tunnels with iBGP

James,

So, are you saying that the debug ip packets is an added verification
that the acl is working properly, not something I would do instead of
using the acl?

Can using the debug ip packet (or maybe, debug ip bgp events ?) indicate
if the tunnel is being used if I don't use the acl?

Tim

----- Original Message -----
From: "James" <james@towardex.com>
To: "ccie2be" <ccie2be@nyc.rr.com>
Cc: "'Brian McGahan'" <bmcgahan@internetworkexpert.com>; "'Group Study'"
<ccielab@groupstudy.com>; <samccie2004@yahoo.co.uk>
Sent: Friday, August 06, 2004 11:54 AM
Subject: Re: Using Tunnels with iBGP

> > int tun 0
> > ip add y.y.y.y
> > tun source s0
> > tun dest y.y.y.z
> >
> > int s0
> > ip access-group # <---- blocks bgp traffic
>
> Yup. Just make sure s0 is the transiting interface on behalf of tun0,
> in
which
> in your config, it is :)
>
> >
> > Now, if the neighbor comes up, I know that it's using the tunnel
> > because
the
> > physical int is blocking bgp traffic. Is this correct?
>
> Right. what you want to do to speed up the observation: clear ip bgp *

> Let the bgp session clear and watch it come back up. It may take a
> little
while
> as usual as FSM needs to react to connectivity collisions as usual.
> But if
its
> taking more than 2 minutes, then check the acl to see if its blocking
something
> although it shouldn't if you use the one I mentioned.
>
> >
> > With your other suggestion, debug ip packets, what is the output I
should
> > look for?
>
> As long as BGP pkts traverse over the tunnel peering, you will see
> 'permit
ip
> any any' incrementing hits while you should really NOT be seeing any
> hits
under
> deny port 179 rules on the acl applied to s0. If you do, that means
> bgp is somehow trying to send a bgp packet over to s0, that is bad
> news.
>
>
> >
> > Thanks alot for your help.
>
> No prob!
>
> >
> > BTW, have you set a date for your lab?
>
> Not sure yet, I am deciding tomorrow actually. I am thinking of
mid-september
> for my 2nd attempt by may change. How about you?
>
> -J
>
> --
> James Jun TowardEX
Technologies, Inc.
> Technical Lead Network Design, Consulting, IT
Outsourcing
> james@towardex.com Boston-based Colocation &
Bandwidth
Services
> cell: 1(978)-394-2867 web: http://www.towardex.com , noc:
www.twdx.net



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