Subject: [Isis-wg] No MAC Address ..

From: Abhishek Verma <[email-masked]>
Date: Tue, 26 Oct 2004 13:47:37 +0530

Hi,

I have an ISIS adjacency (L1/L2/L1L2) up with a router. What if i dont
recieve my MAC address in his HELLOs. What should i do? Should i break
off the adjacency that i have with the other router? What should i do?

Thanks,
Abhishek

--
Class of 2004
Institute of Technology, BHU
Varanasi, India

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From: Tony Li <[email-masked]>
Date: Tue, 26 Oct 2004 01:47:24 -0700

If you don't receive a MAC address (presumably you're on a LAN ;-),
then the other system has broken its adjacency with you, probably 
because
it can't hear you, or it rebooted, and you need to restart the 
adjacency.

Tony

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From: "Parker, Jeff" <[email-masked]>
Date: Tue, 26 Oct 2004 10:19:00 -0400

It isn't clear if
    o He had your MAC address in the past, but no longer does
    o He has never had your MAC address.

If he has never acknowledged you, you could use whatever diagnostic tools
that the peer supports to check for dropped hellos: they may be due to a
number of causes: mismatch of IP address, mismatch of Area Address, mismatch
of security, etc.  You might, for example, be reporting the wrong MAC
yourself.  There may be some diagnostic capability on the peer that will
give you some visibility here.  You are presumably on a LAN, and may have
the ability to perform a packet dump on the hellos.  I would compare the
fields above and look for differences.

We have tried to address this kind of issue with SNMP Notifications and
counters, but that work is recent enough that I would be surprised if it
were implemented on your peer.

- jeff parker

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From: Abhishek Verma <[email-masked]>
Date: Tue, 26 Oct 2004 20:52:14 +0530

Hi Jeff,

>    o He had your MAC address in the past, but no longer does

He had the MAC and my adjacency was up. But then I receive a HELLO
from him in which he doesnt list my HELLO!

And Yes, i am on a LAN. I believe in such cases, i should change my
adjacency from the "UP" state to the "Init" state.

Dont think its mentioned anywhere in the ISIS docs.

Regards,
Abhishek

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From: "Parker, Jeff" <[email-masked]>
Date: Tue, 26 Oct 2004 11:38:04 -0400

> Dont think its mentioned anywhere in the ISIS docs.

Abhishek -
    A serious charge indeed.

    I take it that you are implementing your own version of the protocol.
Does this happen time after time, or rarely?  Does his adjacency move from
state init to full?  Who is the designated router on the LAN?  If it is you,
are you doing the right things?  What happens when you alter the priority so
that the remote end is (or isn't) the DIS?

    I would take a look at what the two of you are sending, as suggested
before.  You might wish to compare your exchange with what two other peers
are doing.  

- jeff parker

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From: "Parker, Jeff" <[email-masked]>
Date: Tue, 26 Oct 2004 11:38:04 -0400

Abhishek -
    A serious charge indeed.

- jeff parker

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From: Abhishek Verma <[email-masked]>
Date: Tue, 26 Oct 2004 21:52:28 +0530

Hi Jeff,

>    A serious charge indeed.

:)

>    I take it that you are implementing your own version of the protocol.

Exactly.

> that the remote end is (or isn't) the DIS?

It happens only when the router at the other end because of some
reason isnt able to process my HELLO messages and times out. I am btw
the DIS, so i have a smaller HOLD Timer than him. This router at the
other end is busy and times out. He then sends me a HELLO message in
which i am not listed.

SO the question is, should i upon recieving this HELLO message bring
down my adjacency with this guy from Up to Init? The doubt came
because its not clearly spelled out in the specs!

Regards,
Abhishek

--

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From: Jeff Learman <[email-masked]>
Date: Tue, 26 Oct 2004 12:34:29 -0400

By George, I think he's right.  While it might be mentioned
somewhere, it should be mentioned in Section 8.4.2.4, "Existing
Adjacencies".

Jeff

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From: "Parker, Jeff" <[email-masked]>
Date: Tue, 26 Oct 2004 12:38:01 -0400

I haven't seen chapter and verse in the two trips to 10589 this morning, but
I wouldn't claim that it isn't covered.

I would suggest that you not use a hello without your MAC to update your
adjacency.  As a result, you will time out soon enough.

    "The router is busy and times out.  He then sends a hello..."

If the router cannot keep up with your hello packets, his adjacency will
time out.  At this point, he tears down the adjacency, so he shouldn't send
your mac address.  Would the router at the far end by your implementation?
What provisions have you made to expedite the sending and receiving of
hellos?  Your body will shortchange your hands and feet to keep your brain
alive.  

- jeff parker

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From: Abhishek Verma <[email-masked]>
Date: Tue, 26 Oct 2004 22:19:35 +0530

> adjacency.  As a result, you will time out soon enough.

why waste time? Why not bring down the adjacency immediately and
declare the remote router to be in the down state.

> your mac address. 

Which is exactly what is happening. Say R1 and R2 are two routers
where R1 is the DIS. R2 waits for some 10 secs and if he doesnt hear
from R1 then he declares him dead, tears down its adjacency and omits
his MAC from its HELLOs. R1, otoh, needs to wait for 30 secs or so, as
per your suggestion to declare R2 to be down. I say, why wait for that
much time. The first time you hear from R1 without your MAC, bring
down the adjacency and go, sing out a song in the rain!

Regards,
Abhishek.

> Would the router at the far end by your implementation?

--

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From: Les Ginsberg <[email-masked]>
Date: Tue, 26 Oct 2004 10:23:57 -0700

Abhishek -

The relevant section in ISO 10589:2002 is:

8.4.2.5.3 If a Level n LAN IIH PDU is received from neighbour N, and this 
system's lANAddress is no longer in N's IIH PDU, the IS shall

a)      set the adjacency's adjacencyState to "initialising", and
b)      generate an adjacencyStateChange (Down) event.

It probably would have been clearer if this text was part of Section 
8.4.2.4 (Existing adjacencies). Nevertheless, it applies in this case.

    Les

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From: Dave Katz <[email-masked]>
Date: Tue, 26 Oct 2004 11:17:26 -0600

See 8.4.2.5.3 in the 1992 spec (the One True Spec.)  Not exactly in the 
right place, but it's there.