[cisco-bba] IOS upgrade kills Linksys

Dennis Peng dpeng at cisco.com
Fri Oct 8 17:27:38 EDT 2004


If you remove it, it won't take effect until the entire L2TP tunnel
goes down and comes back up.

Dennis

Krzysztof Adamski [k at adamski.org] wrote:
> I did have "ip mtu adjust" and I removed it, but that did not help.
> The client has 5 locations, so far in one he upgraded the firmware on the
> linksys and that fixed it, but the other four are not working with the new
> firmware. At the second location he replaced the linksys with a gnet box,
> so far it is working, we will give some time to make sure that is the
> solution before the other locations are changed to gnet.
> 
> Somebody here recommended that I add "qos pre-classify" to the
> virtual-template, that seem to fix a vpn between a linksys and netgear for
> a different customer, I'm really curios why.
> 
> K
> 
>  On Fri, 8 Oct 2004, Dennis Peng wrote:
> 
> > Do you have "ip adjust mtu" under the VPDN group? That will change the
> > MTU automatically, but having a lower MTU can cause problems for some
> > applications. I usually recommend customers to remove it if they are
> > having MTU issues.
> >
> > Dennis
> >
> > Krzysztof Adamski [k at adamski.org] wrote:
> > > I upgrade my LNS from 12.2(12f) to 12.2(15)T14, and now some LinkSys boxes
> > > are showing weird behaviour. The LNS is doing PPPoE aggregation.
> > >  All the normal web access is working, but a VPN access to an exchange
> > > server is not. The VPN software is running on a PC behind the LinkSys. The
> > > VPN packets are encapsulated in UDP.
> > >  Not all VPN is the problem just the exchange traffic. Snooping the
> > > traffic it appears that the exchange is sending a 18k size UDP packet that
> > > is being fragmented. The size of each fragment is 1492 bytes. For some
> > > strange reason the MTU on the virtual-interface is 1464, this is how my
> > > virtual-template looks:
> > >
> > > interface Virtual-Template1
> > >  ip unnumbered FastEthernet1/0
> > >  no ip proxy-arp
> > >  mtu 1492
> > >  ip tcp adjust-mss 1300
> > >  no logging event link-status
> > >  peer default ip address pool ADSL
> > >  ppp authentication pap
> > >
> > > I have tried ip mtu 1492, mtu 1500, mtu 1464, even changing the MTU on the
> > > LinkSys to 1464 nothing helped.
> > >
> > > Any ideas what can be wrong?
> > >
> > > K
> > >
> > >
> > > _______________________________________________
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> > > cisco-bba at puck.nether.net
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> >


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