We have branch office connecting to head quarter by DMVPN.
While we found problem on some office, when ping the WAN interface IP, the latency is normal but when ping the tunnel IP, the latency is very high (40ms vs >200ms). However, not all branch office have the same problem
According to the diagram, for example.
Ping from WAN IP 1 to WAN IP 2, the latency is around 40ms, but ping from Tunnel IP 10.1.1.1 to 10.1.1.2, the latency will >200ms
Ping from WAN IP 1 to WAN IP 3, the latency is around 40ms, ping from Tunnel IP 10.1.1.1 to 10.1.1.3, the latency remains around 40ms
Both router using 1841, and this issue happens suddenly, already tuned MTU size but no help. What other item can I check to fix this issue?