From: Kenneth Wygand (KWygand@customonline.com)
Date: Fri Apr 23 2004 - 10:08:50 GMT-3
I don't really understand the point of making an interface "passive"
under IS-IS. I thought IS-IS does _not_ advertise directly connected
routes natively without the redistribute connected command? So if you
are going to make the interface "passive" so hellos and routing updates
are not sent out that interface, and enabling the interface in the IS-IS
process does not advertise the directly connected network into the
process, what is the difference between enabling IS-IS on a "passive"
interface or instead just not enabling IS-IS on that interface?
Kenneth E. Wygand
Systems Engineer, Project Services
CISSP #37102, CCNP, CCDP, ACSP, Cisco IPT Design Specialist, MCP, CNA,
Network+, A+
Custom Computer Specialists, Inc.
"The only unattainable goal is the one not attempted."
-Anonymous
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
R&S Groupstudy
Sent: Friday, April 23, 2004 4:07 AM
To: Ahmed Mustafa; ccielab@groupstudy.com
Subject: RE: Passive interfaces in ISIS
Passive interfaces depress the transmission of routing protocol packets.
When you enables up ip router isis, and passive-interface on router1,
you
advertised r1's S1 subnet into the isis routing process. Router 2 should
therefore have a route to reach S1 in router3. Router 3 however, will
not
have a router back to R2 since it does not form an adjacency with Router
1.
Try adding a static on R3 for R2 S0; R2 should then be able to ping R2
s1
Adam
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Ahmed Mustafa
Sent: 23 April 2004 08:53
To: ccielab@groupstudy.com
Subject: Passive interfaces in ISIS
Passive intereface in ISIS means actually means that advertise the
network
internally without sending any hello packets.
I am wondering if Passive interfaces can only be assigned for stub
networks
or
loopback networks.
The thing I tested was little wiered.
I connected my routers such as:
R2-----------------------------------R1----------------------------
--R3
R1 and R2 are connected via S0 at both ends, and R1 and R3 are connected
via
S1 at both ends.
I tried this configuration:
On R1,
I tried this:
First I didn't enable "IP ROUTER ISIS" on R1's either S0 or S1,
router isis
net 49.0010.0001.0001.0001.00
passive interface s0------------------------> router didn't like, and
gave
the error message something 'INVALID COMMAND IF CLNS ONLY".
I then enabled the command "IP ROUTER ISIS" on S1 only.
I tried again to above configuration
router isis
net 49.0010.0001.0001.0001.00
passive interface s0------------------------> command was accepted.
I concluded that in order to advertise networks through passive
interfaces
one
of the router's interfaces must be enabled with 'IP ROUTER ISIS"
But again, passive interface will not work on the link between two
routers.
It is only meant for stub networks.
Regards,
Ahmed
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