Is information transmitted over Cisco routers saved anywhere on the router itself?

Question

Everything is in the title: Is information transmitted over Cisco routers saved anywhere on the router itself?

Answer 1

Sure, for microseconds it lives in some buffers so that the routers can check it against ACLs and match it against its routing tables (technically it only needs the headers for performing these actions, and thus could do it on a cut-through method), or buffering it for a slower connection on another link.

If there is ethernet in the mix, it will likely live in a store-and-forward buffer for a few microseconds as well.

If the router is running a packet capture, then there is the potential for some or all of the data matching the capture rules to be stored.

Depending on the logging that's enabled, you might get a few points of metadata stored in the logs as well (although this is most commonly in firewalls).