topic Re: Retransmmision of packets in Firewall and Security Management

Retransmmision of packets

Daniel_Serrano1 — Thu, 18 Feb 2021 00:13:56 GMT

Hi, communtiy,

Currently we have a cluster with 6400 devices, where when performing various packet captures we notice that we see several retransmissions of packets on several interfaces. We have already checked the drop counters (rx and tx), overruns (tx and rx) , revision with ethtool, revision of the history with cpview tool, interface speed synchronization and even applied a debug for drop packets and all is well.
My question is, can the cluster really retransmit packets or do they really come from other equipment (switches, router, balancer)? , so we noticed that a device in front of the fw has an mtu of 1548 and the fw of 1500, could this be a real cause?

.......mmmmm any idea what could be investigated before involving the TAC?

Regards

Re: Retransmmision of packets

PhoneBoy — Thu, 18 Feb 2021 03:53:06 GMT

Retransmissions can occur as part of TCP and the gateway likely has nothing to do it (unless Src/Dst is the gateway).

Mismatched MTU can cause issues down the road.

Re: Retransmmision of packets

Daniel_Serrano1 — Thu, 18 Feb 2021 05:31:25 GMT

Thanks phoneboy for your prompt reply,
In conclusion if the retransmissions we see are host to host, the gateway does not interfere to the level of retransmitting those packets.

Regards