From: Scott Morris (swm@emanon.com)
Date: Fri Mar 28 2003 - 11:48:01 GMT-3
Many places also use the IP address since that's something a bit more
traceable.
Wait... A 4-byte address into a 6-byte ID? Yup, just expand 'em. For
example 192.1.3.15 becomes 192.001.003.015 and you can break that down
to 19 20 01 00 30 15 for your 6 byte systemID in the NSAP address.
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
adz
Sent: Friday, March 28, 2003 4:14 AM
To: ccie2be; Group Study
Subject: RE: IS-IS NET clarification
Hi,
The OSI protocols is largely used in transmission network management
networks. It's generally good practice in these large networks to use a
system ID that is the same as the MAC address of an Ethernet port on the
device. This is done because :
1. MAC addresses are unique (?)
2a. the system ID needs to be unique - so why not use the mac address?
It's easy to tell an installer to do this. You don't know the MAC
address until install time, do you can't prepare a full NSAP for the
installer to use.
2b. Using the MAC address is more scalable and inplementable than
makeing something up.
3. the ES-ES protocol which does a similar function to IP's ARP, maps
logical addresses to the datalink layer. With the Ethernet medium, it
help in debugging if the logical address and the L2 address are the
same(from a human perspective). Obviously this only works if there is
only one Ethernet port on the device (normal in OSI Network management
networks)
In the LAB, I would be inclined to use a naming scheme that is Quick and
easy for you to implement. In may well be quicker to use for example
xx.xxxx.1111.1111.1111.00 for R1 and xx.xxxx.2222.2222.2222.00 for R2
and so on.
cheers...
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
ccie2be
Sent: 26 March 2003 21:44
To: Group Study
Subject: IS-IS NET clarification
Hi,
I hope this isn't a silly question.
In Doyle's book, he says that usually the NET is made up from the area
ID with the MAC address appended to it.
I'm wondering is this a rule or a suggestion? And, if it's a rule, does
it matter which MAC address is used?
Since the NET in ISIS is comparable to the Router ID in OSPF and applies
to the router as a whole, it seems to me it shouldn't matter what MAC
address is used. And, taking that 1 step further, if it doesn't matter
what MAC address is used, perhaps it doesn't matter if a MAC address is
used at all.
Please set me straight on this. Thanks, Jim
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