12-20-2023 12:24 PM
Hi Team,
I just want to know its just a normal behavaiour - Does it 10 seconds to become active?
12-20-2023 02:02 PM
HSRP adjacency formation involves routers exchanging hello messages to discover each other's presence and determine the active and standby roles. The hello messages are part of the HSRP timers, including the hello interval and hold time.
Lowering the hello interval allows for faster detection of neighbor routers and can speed up the convergence process. However, there is a practical limit. Even with very short hello intervals, the overall convergence time is constrained by the routers' processing capabilities, including CPU power and other internal processes...
12-20-2023 02:32 PM
Final config
hostname SW1
ip dhcp pool 1
network 10.10.1.0 255.255.255.0
dns-server 8.8.8.8
default-router 10.10.1.3
spanning-tree mode pvst
spanning-tree extend system-id
spanning-tree vlan 1 priority 24576
!
vlan internal allocation policy ascending
!
interface Ethernet0/0
!
interface Ethernet0/1
switchport trunk encapsulation dot1q
switchport mode trunk
!
interface Ethernet0/2
!
interface Ethernet0/3
!
interface Vlan1
ip address 10.10.1.1 255.255.255.0
standby version 2
standby 0 ip 10.10.1.3
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server
!
!
!
!
!
!
control-plane
!
!
line con 0
logging synchronous
line aux 0
line vty 0 4
login
!
!
hostname SW2
spanning-tree mode pvst
spanning-tree extend system-id
spanning-tree vlan 1 priority 28672
!
vlan internal allocation policy ascending
!
interface Ethernet0/0
!
interface Ethernet0/1
!
interface Ethernet0/2
!
interface Ethernet0/3
!
interface Vlan1
ip address 10.10.1.2 255.255.255.0
standby version 2
standby 0 ip 10.10.1.3
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server
control-plane
!
!
line con 0
logging synchronous
line aux 0
line vty 0 4
login
!
!
end
SW2#
12-20-2023 08:49 PM
now how many packet you lose ?
MHM
12-21-2023 02:19 PM
I dont see any major changes in failover even I changed the timers
12-21-2023 11:23 PM
Now we still have two option
1-Use router port instead of vlan svi
2-Use bfd (note bfd in gns3 not work it can crash your router in lab)
MHM
12-22-2023 06:19 AM
Just to confirm, you revised all HSRP interface timer config settings, correct?
Is this being done on real hardware or on an emulator? If the latter, actual switch over times will depend much on the emulator.
12-22-2023 07:35 AM
@Joseph W. Doherty Yes I set the timer on VLAN 1 which is currenly setup for HSRP.
I am using EVE-NG for my lab
12-22-2023 07:47 AM
Use bfd if you not use gns3.
Do this in both L3SW HSRP
-Standby bfd all interface (global)
-Under interface
Standby bfd
-Under interface
Bfd interval 50 mix 50 multi 3
12-22-2023 08:09 AM
"Timer" singular?
Just to reconfirm, you set the HSRP hello and hold timers the same on all (two?) interfaces in the same group, correct?
Unable to say how impactful EVE-NG might be, but have over the decades have effectively used HSRP with reduced timers on real devices.
12-22-2023 08:18 AM - edited 12-22-2023 08:18 AM
About suggestions of change timer' the rtt is in "ms" and timer is in "s"
So even small timer make him see icmp drop.
So we need to make change faster by use bfd which is also in ms
Or change the interface to l3 which make it down immediately' notice he use vlan so it need to detect l2 port to down before vlan is down.
@ankitohc we started with 10 loss now it 5 loss continued to be one or two.
MHM
12-22-2023 09:25 AM - edited 12-22-2023 09:25 AM
@MHM Cisco World @Joseph W. Doherty This is what I have done standby 0 timers msec 100 msec 350
I did not notice single drop.. check attach GIF..
12-22-2023 09:34 AM
Now you use ms that sure solve issue.
We need to make timer less than rtt of ping' and you get it.
Good job friend
Have a nice day
MHM
12-22-2023 09:38 AM
@MHM Cisco World @Joseph W. Doherty I really appricate your support to fix this issue and some basic understanding of HSRP.
Thanks
12-22-2023 09:40 AM
friend you are so welcome any time
MHM
12-22-2023 09:52 AM
That's good, although you keep showing but one interface. The reason I keep trying to confirm you've reconfigured all HSRP interfaces is this little nugget in the reference I earlier provided:
The timers configured on the active device always override any other timer settings. All devices in a Hot Standby group should use the same timer values.
Assuming your earlier reduced timer test, which appeared to not correctly work, was in fact correctly configured, interactions with emulator can cause odd issues. I.e. different code paths might be involved. Since you're now using millisecond timers, then the following might apply:
The HSRP BFD Peering feature introduces Bidirectional Forwarding Detection (BFD) in the Hot Standby Router Protocol (HSRP) group member health monitoring system. HSRP supports BFD as a part of the HSRP group member health monitoring system. Without BFD, HSRP runs as a process in a multiprocess system and cannot be guaranteed to be scheduled in time to service large numbers of groups with hello and hold timers, in milliseconds. BFD runs as a pseudopreemptive process and can therefore be guaranteed to run when required. Only one BFD session between two devices can provide early failover notification for multiple HSRP groups.
This feature is enabled by default.
Interesting too, is @MHM Cisco World's mention you need to use BFD. (In my past experience, I recall using HSRPv2 and millisecond timers before BFD was supported on many platforms, and subsecond switchover was often impractical.)
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