GRE thru pix

[rnutter]

what ports and protocols should be enabled on a pix to allow a gre tunnel between company a and company b internal routers across the internet?

[scoclayton]

GRE is protocol number 47. It is not a TCP or UDP based protocol so it therefore does not have layer 4 (port) information. The PIX will recognize the name 'gre' in any access-list entry. An example would be:

access-list 101 permit gre host 1.2.3.4 host 5.6.7.8

Hope this helps.

Scott