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RE: [j-nsp] isis question

  • From: MPuras@solunet.com
  • Date: Wed, 25 Apr 2001 16:49:25 -0400
  • Resent-Date: Wed, 25 Apr 2001 18:15:24 -0400
  • To: chris.flores@onfiber.com, MPuras@solunet.com, zjgu@ce-air.com, mpls-ops@mplsrc.com, juniper-nsp@puck.nether.net, aviva@juniper.net

I had to verify the answer for the first question.  I have posted it below:
 
QUESTION:
 
1  Which network layer use to encapsulation isis-pdu?
Is it clnp or ip? 
 
 
ANSWER:

ISIS PDU's are not encapsulated in IP. Like IP, CLNP (often referred to as OSI) runs at the network-layer. It is often stated that IS-IS runs directly over the data-link (L2) protocol. However, IS-IS uses CLNP packet types.

 

 

Mario Puras
SoluNet Technical Support
Network Support Engineer
We don't make network products,
we make them Work!
Mailto:mpuras@solunet.com
888.SOLUNET (Canada) / 888.449.5766 (USA)

-----Original Message-----
From: Chris Flores [mailto:chris.flores@onfiber.com]
Sent: Wednesday, April 25, 2001 4:39 PM
To: 'MPuras@solunet.com'; zjgu@ce-air.com; mpls-ops@mplsrc.com; juniper-nsp@puck.nether.net; aviva@juniper.net
Subject: RE: [j-nsp] isis question

I agree, this becomes a matter of semantics. I stated in my email that a single p2p link connecting to a neighbor establishes one adjacency. A level-1/level-2 IS (router) implies a minimum of two p2p links, one connecting to a level-1 IS and another connecting to a level-2 IS. Thus, two neighbors and two adjacencies. I was taking a simpler approach to my email :-) Thank you for the clarification...
 
Best regards.
 
Chris 
-----Original Message-----
From: MPuras@solunet.com [mailto:MPuras@solunet.com]
Sent: Wednesday, April 25, 2001 11:12 AM
To: Chris Flores; zjgu@ce-air.com; mpls-ops@mplsrc.com; juniper-nsp@puck.nether.net; aviva@juniper.net
Subject: RE: [j-nsp] isis question

#2.  

Depends - I believe by default L1/L2 is enabled on Juniper, therefore 2 adjacencies. Otherwise, if L1 only or if L2 only, then only a single adjacency.

 

Mario Puras
SoluNet Technical Support
Network Support Engineer
We don't make network products,
we make them Work!
Mailto:mpuras@solunet.com
888.SOLUNET (Canada) / 888.449.5766 (USA)

-----Original Message-----
From: Chris Flores [mailto:chris.flores@onfiber.com]
Sent: Wednesday, April 25, 2001 10:59 AM
To: 'zheng jiang gu'; mpls-ops@mplsrc.com; juniper-nsp@puck.nether.net; Aviva Garrett
Subject: RE: [j-nsp] isis question

My response is in-line. I hope it helps...
-----Original Message-----
From: zheng jiang gu [mailto:zjgu@ce-air.com]
Sent: Tuesday, April 24, 2001 9:15 PM
To: mpls-ops@mplsrc.com; juniper-nsp@puck.nether.net; Aviva Garrett
Subject: [j-nsp] isis question

hi all:
   When I study isis, I meet the problem:
1  Which network layer use to encapsulation isis-pdu?
Is it clnp or ip? 
 
CF: The OSI packets (or PDUs) are forwarded "as is" or transmitted directly over the underlying link layer without the need for encapsulation - per RFC 1195.
 
2  How many IS-IS adjacency between point-to-point routers?
 
CF: IIH (IS-IS Hello) PDUs are utilized to initialize and maintain adjacencies between neighbors. On a p2p link, one neighbor creates one adjacency. Do you have a more specific question that needs answering?
 
br
shawn