From: Leigh Harrison (leigh.harrison@azzu.co.uk)
Date: Thu Sep 08 2005 - 10:47:23 GMT-3
Bob,
You're bang on.
You do need the "preempt" command in there. By default the "track"
command will take 10 off your priority, but if you're not telling the
router/switch to do anything with it when the priority drops below one
of its peers, then it won't !!
I ran a quick test:-
r3#sh stand
FastEthernet0/0 - Group 1
State is Active
5 state changes, last state change 00:01:26
Virtual IP address is 1.0.0.254
Active virtual MAC address is 0000.0c07.ac01
Local virtual MAC address is 0000.0c07.ac01 (v1 default)
Hello time 3 sec, hold time 10 sec
Next hello sent in 2.552 secs
Preemption disabled
Active router is local
Standby router is 1.0.0.252, priority 101 (expires in 9.568 sec)
Priority 100 (configured 110)
Track interface Serial0/0/0 state Down decrement 10
IP redundancy name is "hsrp-Fa0/0-1" (default)
Note the "Track interface Serial0/0/0 state Down decrement 10" -
normally it should be state "Up" if all things were well. BUT the
router still thinks that he's the Active - because nobody has the power
to tell it otherwise.
FYI:
r5#sh stand
Ethernet0 - Group 1
Local state is Standby, priority 101
Hellotime 3 holdtime 10
Next hello sent in 00:00:01.644
Hot standby IP address is 1.0.0.254 configured
Active router is 1.0.0.253 expires in 00:00:08
Standby router is local
Hope that helps,
LH
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Bob Nelson
Sent: 08 September 2005 03:19
To: ccielab@groupstudy.com
Subject: HSRP and Track - 3550
Hello All:
I want to make sure I am clear on the preempt and track for HSRP.
Here is an example from the DocCD. My questions follow the example
In the following example, the tracking process is configured to track
the IP routing capability of serial interface 1/0. HSRP on Ethernet
interface 0/0 then registers with the tracking process to be informed of
any changes to the IP routing state of serial interface 1/0. If the IP
state on Serial interface 1/0 goes down, then the priority of the HSRP
group is reduced by 10.
If both serial interfaces are operational, then Router A will be the
HSRP active router because it has the higher priority.
However, if IP routing on serial interface 1/0 in Router A fails, then
the HSRP group priority will be reduced and Router B will take over as
the active router, thus maintaining a default virtual gateway service to
hosts on the 10.1.0.0 subnet.
Router A Configuration
track 100 interface serial1/0 ip routing !
interface Ethernet0/0
ip address 10.1.0.21 255.255.0.0
standby 1 ip 10.1.0.1
standby 1 priority 105
standby 1 track 100 decrement 10
Router B Configuration
track 100 interface serial1/0 ip routing !
interface Ethernet0/0
ip address 10.1.0.22 255.255.0.0
standby 1 ip 10.1.0.1
standby 1 priority 100
standby 1 track 100 decrement 10
1. "If both serial interfaces are operational, then Router A will be the
HSRP active router because it has the higher priority."
Is this necessarily true. Does it not depend on which interface
was brought up first?. Without preempt, A will not become active if it
is brought up second, correct?
Without the preempt command on Router A, it will not take over
just by virtue of the higher priority.
2. "if IP routing on serial interface 1/0 in Router A fails, then the
HSRP group priority will be reduced and Router B will take over as the
active router"
Again, just because the priority on A (assuming it is the active)
drops below router B's priority, does not mean it will take over as
active,
without B having preempt configured. Additionally, if B is
configured
to preempt A when Serial 1/0 goes down on router A, so it become the
active,
A must also have preempt configured to resume its active role when
the
serial comes up.
Is this correct and they just did not put the preempt statements for
brevity(confuse me) or am I missing the concept.
Thanks for the help. Sorry for the length, wanted to be complete
This archive was generated by hypermail 2.1.4 : Sun Oct 02 2005 - 14:40:14 GMT-3