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New Member

a simple question of EIGRP.

Hi. everyone..

I have a problem related EIGRP on running at Cisco.

The most I wonder is that Does EIGRP use a Layer 4 Port as tcp/udp?, It is not definitly Right?

It just a Layer 3 Protocol for update to its neighbor EIGRP router. So It's not use tcp / udp to update routing update.

If my opinion is wrong, please fix it for me

Thank in advance.

1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Re: a simple question of EIGRP.

Hello,

The EIGRP does not use ports. The reason is that EIGRP uses its own transport protocol called Reliable Transport Protocol (protocol number 88) which does not use ports. This protocol was designed because of two reasons:

1.) To make EIGRP independent of the actual Layer3 protocol. As you know, the EIGRP exists for IPX, IPv4 and IPv6 but the transport protocol remains the same.

2.) Perhaps even more importantly, EIGRP needs a transport protocol that provides reliable services and multicast delivery at the same time. The TCP is reliable but does not support multicasts. The UDP does provide multicast capability but does not provide reliability. The Reliable Transport Protocol provides both.

Because the Reliable Transport Protocol was designed specifically with EIGRP in mind, it does not need to use ports, which are so or so specific to the TCP/IP stack.

Best regards,

Peter

2 REPLIES
New Member

Re: a simple question of EIGRP.

short answer is no.

a bit longer answer is it use RTP.

Cisco Employee

Re: a simple question of EIGRP.

Hello,

The EIGRP does not use ports. The reason is that EIGRP uses its own transport protocol called Reliable Transport Protocol (protocol number 88) which does not use ports. This protocol was designed because of two reasons:

1.) To make EIGRP independent of the actual Layer3 protocol. As you know, the EIGRP exists for IPX, IPv4 and IPv6 but the transport protocol remains the same.

2.) Perhaps even more importantly, EIGRP needs a transport protocol that provides reliable services and multicast delivery at the same time. The TCP is reliable but does not support multicasts. The UDP does provide multicast capability but does not provide reliability. The Reliable Transport Protocol provides both.

Because the Reliable Transport Protocol was designed specifically with EIGRP in mind, it does not need to use ports, which are so or so specific to the TCP/IP stack.

Best regards,

Peter

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