That makes sense. I also noticed this really starting when the CPU is
heavily nailed. (looking at the time this started against some graphs).
Sounds reasonable I can try to bring the link up with the loop unloaded to
see if that helps but I still sort of feel possible MTU issues but can't put
my finger on it. Some more googling shows that there can be issues if
path-mtu-discovery and timestamps are enabled at the same time but I don't
have a tcp timestamps entry in the global config.
-----Original Message-----
From: David Prall
Sent: Thursday, July 21, 2011 4:28 PM
To: Scott Granados ; [email protected]
Subject: RE: [c-nsp] BGP "keep alives throttled do to tcp", MTU mismatch?
BGP Hellos are not sent with pak-priority, while they are marked IP
Precedence 6. Thus they need to be prioritized if you have a congested link.
That GE Port on the NPE-400 is subrate to begin with, so you could be
dropping them before they even make it out or can be processed inbound.
David
--
http://dcp.dcptech.com
-----Original Message-----
From: [email protected] [mailto:cisco-nsp-
[email protected]] On Behalf Of Scott Granados
Sent: Thursday, July 21, 2011 4:01 PM
To: [email protected]
Subject: [c-nsp] BGP "keep alives throttled do to tcp", MTU mismatch?
Hi, I have a puzzler.
I have two Cisco 7206VXr routers one with a G1 and the other with a 400
processor.
Between them terminated on a gig interface on each side is an ILEC
provided metro E connection that’s pretty vanilla using VLANs to
address different connections.
I have a /30 set up on a common VLAN between the two with the BGP peer
set up on that /30.
After 3 minutes, my session will reset I’m assuming do to lack of
keepalives / problems with MTU. Lots of googling as pointed me at
various MTU mismatch situations but I’m not sure what I’m doing wrong
possibly assuming something is set “in an interesting way” between the
sites on the ILEC network.
On each interface I have the following
int gig x/x
mtu 1522
Assuming 1500 for standard Ethernet and 22 for the VLAN tags.
I also have the following set in global mode
ip tcp path-mtu-discovery
On both VXR devices code 12.4-25C is being run.
I would appreciate any pointers to investigate. What have I
missed?
Thanks
Scott
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