[c-nsp] Multicast Packet Loss over GRE

[Benjamin Lovell]

If it's enough / consistent enough packet drops you should be able to see a diff on the two tunnel routers in "sh ip mroute x.x.x.x x.x.x.x count". This should at least confirm where the drops are happing. 

Mcast packet forwarding is not significantly different for being over a GRE tunnel if we are talking about a software router (do normal mcast stuff then hand off for encap or decap then hand to mcast code). Hardware platforms on the other hand are a diff story.

-Ben


On Feb 24, 2011, at 12:07 AM, Dav A wrote:

> Hi All, 
> 
> Was hoping someone can provide some advice with regards to troubleshooting a 
> particularly painful multicast issue. 
> 
> 
> The set up isnt particularly complex:
> 
> Servers <>Switch<>Tunnel router (RP) >>>>> GRE over WAN >>>> Tunnel router 
> <>Switch<>Servers
> 
> The tunnel router interfaces have been configured with the TCP mss adjust mtu 
> command and set to 1400. 
> 
> 
> Everythings been up and working for a year but recently weve been experiencing 
> issues with mcast and can see dropped packets when using a sniffer on the 
> server. The suspicion lies with the WAN provider who has recently made changes 
> but extended pings/sweeps over the WAN shows no drops.
> 
> Has anyone any ideas or experience on how to troubleshoot packet loss over GRE 
> for multicast? 
> 
> 
> Regards, David
> 
> 
> 
> 
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