Re: GRE Tunnels and MPLS

[Shimol Shah <shimshah () cisco com>]

What exact commands did you add to get the MPLSoGRE working ? If you 
remove them do the web traffic issues stop ? Is the traffic narrowed to 
being dropped by the 7600 ?

Shimol

On 11/9/10 8:04 PM, Rettke, Brian wrote:
> It appears that about half of our web traffic is now being dropped, so problems continue. I'll have to double check MTU and 
> TCP adjust-mss settings, but other than that I have no idea. I've heard that there are some issues with MPLS using some of 
> the 67xx linecards, and apparently this is going to be a huge problem for us.
> ________________________________________
> From: Shimol Shah [shimshah () cisco com]
> Sent: Monday, November 08, 2010 1:19 PM
> To: nanog () nanog org
> Subject: Re: GRE Tunnels and MPLS
>
> Good deal. Sounds like a plan.
>
> Shimol
>
> On 11/8/10 2:00 PM, Rettke, Brian wrote:
> > This seems to be working now with the 'mls mpls tunnel-recir' command entered. There are some potential downsides, but 
> > this should get things up and running until I create the new backup tunnels (GRE over IPSec) on a connected router that is not 
> > MPLS-enabled. Thanks!
> >
> > Sincerely,
> >
> > Brian A . Rettke
> > RHCT, CCDP, CCNP, CCIP
> > Network Engineer, CableONE Internet Services
> >
> >
> > ------------------------------
> >
> > Message: 6
> > Date: Thu, 04 Nov 2010 16:49:55 -0400
> > From: Shimol Shah<shimshah () cisco com>
> > Subject: Re: GRE Tunnels and MPLS
> > To: nanog () nanog org
> > Message-ID:<4CD31C73.80004 () cisco com>
> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> >
> > Do you have recir enabled ? If not, good one to enable and check for
> > status of issue.
> >
> > http://www.cisco.com/en/US/docs/ios/mpls/command/reference/mp_m1.html#wp1012208
> >
> > "If you do not enable tunnel-MPLS recirculation, the IPv4 and
> > IPv4-tunneled packets that need to be labeled (for example, the packets
> > that are encapsulated with an MPLS header) will be corrupted when they
> > are transmitted from the Cisco 7600 series router."
> >
> > Shimol
> >
> > On 11/4/10 4:00 PM, Rettke, Brian wrote:
> > > Beginning work on our implementation of MPLS for the backbone network. I've run into difficulty with our GRE tunnels. The GRE 
> > > Tunnel sits on our co-lo router (a Cisco 7600), and it uses a route-map to push our 10.x modem traffic to our DHCP servers. This is 
> > > because the backbone is not complete and DHCP traffic needs to traverse the internet. What I have found is that when I enable basic 
> > > MPLS on the co-location interfaces that head back to the individual systems, DHCP traffic still works, but ICMP and other 10.x traffic 
> > > dies. There is also an intermittent problem with DHCP when it is enabled, where not all DISCOVERS are answered. I've tried 
> > > everything I can think of, including adjusting MTU and TCP MSS. It only seems to impact when the co-location router has a GRE tunnel 
> > > on one buffer, which it terminates, and then it has to encapsulate traffic with an MPLS tag before sending out of the other buffer. 
> > > Theoretically, it should work, but I can't figure out if there is some pr
o
> b
> > lem with MPLS' interaction with the tunnel. Has anyone encountered something similar?
> > > Sincerely,
> > >
> > > Brian A . Rettke
> > > RHCT, CCDP, CCNP, CCIP
> > > Network Engineer, CableONE Internet Services