I'm trying to use "ip tcp mss adjustment" on a GRE Tunnel to force end nodes to reduce their packet size. I've confirgured "ip tcp adjust-mss 1400" on both side of the GRE Tunnel, but the router is still sending ICMP Type 3, code 4 with Next hop MTU=1476. I was expecting to see a smaller Next hop like MTU 1444 bytes.
It is possible that the TCP MSS adjustment works but note that it applies specifically to TCP traffic by modifying the contents of TCP SYN or SYN/ACK segments directly. It does not use ICMP to perform its work. For other kinds traffic (say, UDP or ICMP), the TCP MSS adjustment does not apply.
If you see the ICMP T3C4 messages being sent by your router, can you examine their contents using Wireshark and see what contents do they carry? Usually, they also hold the IP+L4 header of the packet they relate to. I would be interested to see if they still refer to some TCP traffic, or whether the related packet was a non-TCP datagram.
The Next Hop MTU of 1476 is correct for GRE tunnels (1500B - 20B for the new IP header - 4B for the GRE header).
good morning I have this report from users, saying that they encounter connection issue only when they are wired , but the wireless I fine. both connection are using the same path to the internet ...please advised a troubleshooting plan.
Enterprise Switching Business Unit is glad to announce Beta release 16.12.3 for all Catalyst 9200/9300/9400/9500/9600. This release is made available to allow users to test, evaluate and share feedback before General Avail...
Hello.I make tools for gt CDP/LLDP data? VLANs/SVI and connected hosts (MAC/IP/Vendor).Work rfom windows.Can be exported to xml/json filedownload from: http://www.powerc.ru/download/PowerTOOLS.msi (for Windows).If You have questions please contact wi...
Hi there, I'm looking to upgrade the EHWIC-4G-LTE-G SKU MC7710 but i cant find the right firmware, or do I? I feel like I'm running arround in circles:Here I find the upgrade link: Cisco Firmware Upgrade Guide for Cellular Modems: htt...