Here's what's going on: When IP receives a packet (coming up from ethernet or whatever L2 is), it doesn't look at the port number to see where to go next. It looks at the Protocol Number, which indicates which process is next up the OSI model. For example, ICMP is protocol number 1, TCP is number 6, and as you stated below, ESP is 50 and AH is 51. A complete list can be found at: http://www.isi.edu/in-notes/iana/assignments/protocol-numbers Hope this helps - Sincerely, Bradley J. Wilson CCNA, CCDA, MCSE, CCSE, MCT, CTT -----Original Message----- From: George Zhang Sent: 31 August 2000 15:33 To: [EMAIL PROTECTED] Subject: A question about IPSec I read the following form Cisco documentation about IPSec: "IKE uses UDP port 500. The IPSec ESP and AH protocols use PROTOCOL numbers 50 and 51. Ensure that your access-list are configured so that 50, 51 and UDP port 500 traffic is not blocked ..." My question is, what are the PROTOCOL numbers? This is the first time I read or heard about "PROTOCOL number"? I know many protocols by names such as TCP, UDP, ICMP etc, by I have never heard about PROTOCOL numbers? What protocols 50 and 51 are associated with? Could someone please explain that to me? Thanks. George Zhang, CCNP ___________________________________ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
