Hi All,
I have an odd issue...
My WAN is a Native LAN solution. basically, its a L2 VLAN from our ISP.
My Main location has 100mbFiber, ethernet handoff. 3945E rotuer
Branch1 has 10mb Fiber, with ethernet handoff. 2801 router
Branch2 has 3mb Bonded T1s, with Ethernet handoff 2801 router
Branch3-18, same as 1 or 2, depends on the locaiton. 2801 routers
I run DMVPN across the WAn to my branches via Tunnel0 on my routers.
If I try to ping a host at Branch 2 like this: ping <host> -l 1470 -f... Ping completes just fine.
If I try to ping a host at Branch 1 with same parameters, I get a "Packet needs to be fragmented but DF set." from my HQ router.
The Tunnel interfaces on my branch routers are identical:
interface Tunnel0
bandwidth 10000
ip address 192.168.95.x 255.255.255.128
ip access-group 170 in
ip access-group inter-branch out
no ip redirects
ip mtu 1420
ip flow monitor flow-1 input
ip nhrp map multicast xxxxx
ip nhrp map xxxxx
ip nhrp map multicast xxxxx
ip nhrp map xxxxx
ip nhrp network-id 1
ip nhrp holdtime 600
ip nhrp nhs <IP1>
ip nhrp nhs <IP2>
ip ospf network broadcast
ip ospf hello-interval 30
ip ospf priority 0
qos pre-classify
tunnel source FastEthernet0/1
tunnel mode gre multipoint
tunnel key 0
tunnel path-mtu-discovery
tunnel protection ipsec profile GreenDMVPN
Tunnel at Main location, also DMVPN Hub, is this:
interface Tunnel0
bandwidth 100000
ip address 192.168.95.x 255.255.255.128
no ip redirects
ip mtu 1420
ip pim sparse-mode
ip flow monitor flow-1 input
ip nhrp map multicast dynamic
ip nhrp network-id 1
ip nhrp holdtime 600
ip virtual-reassembly in max-reassemblies 1024
ip tcp adjust-mss 1360
ip ospf network broadcast
ip ospf hello-interval 30
ip ospf priority 12
qos pre-classify
tunnel source GigabitEthernet1/0.95
tunnel mode gre multipoint
tunnel key 0
tunnel protection ipsec profile GreenDMVPN
I did debug ip icmp at branch and HQ router... the fragmentation needed messages are for sure being generated from the HQ router.
Any idea WHY I see the different behavior between the branches?
I would think that since my MTU is set at 1420, a packet of 1470 with DF set would die to all branches. Thoughts?
