we have a asa-asa connection between 2 buildings with ipsec and a gre tunnel between them because we use eigrp for this network.the tunnel is ok works perfect but i get syslog messages like :
Aug 13 17:04:54 FWH50031 %ASA-4-313005: No matching connection for ICMP error message: icmp src outside:188.8.131.52 dst inside:184.108.40.206 (type 3, code 4) on outside interface. Original IP payload: <unknown>.
Aug 13 17:05:04 FWH50031 %ASA-6-602101: PMTU-D packet 1462 bytes greater than effective mtu 1434, dest_addr=220.127.116.11, src_addr=18.104.22.168, prot=GRE
and we don't find anything about on cisco to adjust the PMTU-D size on the GRE Tunnel.