I've created a Tunnel between a Cisco 2811 router and a Switch 6509, the tunnel works fine. However, I would like to run Multicast down this tunnel to avoid using a non-supported 3rd party network device that doesn't support multicast. Some of the multicast packets are above 1500 bytes. I would like figure out why the 6509 tunnel does not support frame sizes over 1500 bytes and the 2811 router does. I have applied ip mtu 1576 but this does not really come into play as the packets are UDP. problems seen below:
See the difference with MTU sh int tunnel1 - why is this
Switch config (s72033_rp-IPSERVICESK9-M), Version 12.2(18)SXF13)
ip address 10.210.183.14 255.255.255.252
ip mtu 1576
ip pim sparse-mode
keepalive 2 3
tunnel source Loopback2
tunnel destination 10.210.183.254
Routers config (C2800NM-IPBASEK9-M), Version 12.4(24)T3)
1. configure MTU size on the interface vlan (same VLAN as Tunnel)
2. then go back into the Tunnel and apply the same MTU size, the packet size limitation error does not show up, the show int tun command will still show 1514 bytes
3. I then completed some ping tests over 1500 bytes between tunnel router <>switch and the packets do not fragment. which means in fact the size has been increased to 1575 bytes on the Tunnel interface even though sh inttunnel0 still shows 1514bytes (BUG!)
So success! which means I don't have to upgrade the IOS on my 6509 switches thankfully.
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Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...