RS/960 upgrade ... status report
long at nic.near.net
Fri May 1 04:23:18 UTC 1992
From: William Manning <bmanning at is.rice.edu>
Subject: Re: RS/960 upgrade ... status report
Date: Thu, 30 Apr 92 23:07:02 CDT
observed during RS/960 testing. The problem involved some aberrant
behavior of rcp_routed when a misconfigured regional peer router would
advertise a route via BGP to an ENSS whose next hop was the ENSS
itself. The old rcp_routed could go into a loop sending multiple
redirect packets out on to the subnet. The new rcp_routed will close
the BGP session if it receives an announcement of such a route. The
new rcp_routed software also has support for externally administered
inter-AS metrics, an auto-restart capability, and bug fixes for BGP
overruns with peer routers.
This deployment caused a few problems. One is that this
new feature of rcp_routed pointed out a misconfigured peer router
at Rice University in Houston. This caused the BGP connection to
open and close rapidly which caused further problems on the peer
router. Eventually the peer was reconfigured to remove the
bad route, which fixed the problem. Another problem was on the
Argonne ENSS. This node crashed in such a way that it was
What he did not say:
The new rcp_routed will (virtually) immeadiately after the
close, reopen a BGP session and pump all known routes at the BGP peer.
If the peer is already working on processing the old ones, this adds an
unneeded burden on the regional peer. I have not reviewed the spec in
detail, but there should be something in place to prevent a constant
cycle of close, open, slam 5k routes, close, open, slam 5k routes,
close... well, you get the picture. This points out a configuration
problem with BGP in the ANS T3 routers, in addition to the less than
optimal configuration that we had in our ciscos.
Just my two cents from the other side of the fence.
Given that we haven't heard of anyone else's peer router dying a horrible
death since the new rcp_routed went in, I assume that the "less than optimal
configuration" isn't a *common* mistake. But, for the benefit of those of us
who are soon to run BGP (and who seem to have a knack for encountering uncommon
mistakes :-), can you fill us in on what the actual config problem was? Were
you redistributing your EGP-learned-routes back to BGP or something?
Wouldn't it make more sense for the ENSS to just ignore the offending route
rather than close the BGP session, especially given the lack of a delay before
the session gets reestablished?
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