1. If active interface will down standby will be work as active, but if we would like to configure 3 interface for redundancy for HSRP then what will be the configuration we need to do and what will be interface status for all.
1. Use different groups for different HSRP instances. Active, standby and listen.
2. WHEN HSRP BECOMES ACTIVE / ACTIVE ??
LOGIC IN SIMPLE WORDS ..
How Switches know .. who will be Active .. How they will compare .. Only When they talk to each other ..
If communication is stopped .. due to any reason ..
Then both will think they are alone .. there is no comparison of Priority and Both will declare themself as Active ..
” So Both will be Active ”
1. In VSS/VPC Technology.
2. Issues of ACTIVE/ACTIVE
1. physical link issue
2. one of the trunk interfaces are not forwarding desired vlan for which HSRP is configured
3. HSRP authentication Issue
option number 1 and 2 were observed in real environment. option 3 in lab environment
3. HSRP is using 22.214.171.124 multicast address to communicate between Active and Standby. An Access list can block this address and the communications between the two nodes will stop.If communication between hsrp switches stop. It’s split brain scenario, Both switches will think he’s active.
3. Is it necessary to HSRP active router should be the STP root?
1. Not necessary because we can go HSRP load sharing of vlan on active switches or router but it’s better recommendation to have root bridge.
4. Can we configure HSRP on sub interfaces?
1. Yes, when we assign vlan or subnet to the Sub Interface .. then it will act as Gateway .. similar to Layer 3 Vlan.
5. Case #1: HSRP Standby IP Address Is Reported as a Duplicate IP Address
These error messages can appear:
Oct 17 13:15:41: %STANDBY-3-DUPADDR: Duplicate address 10.25.0.1 on Vlan25, sourced by 0000.0c07.ac19
How to resolve the issue and what are the possibility of Duplicate IP address?
1. Same IP address configured on both active and standby devices, changing the IP at active or standby device will fix the issue.
2. Trace mac address mentioned in logs
6. Does Hsrp, VRRP and GLBP support ipv6?
1. Yes, version 2 for HSRP and GLBP but for VRRP only V3 supported IPv6.
7. How many routers can participate in one group? How many total groups can be formed?
1. Maximum group support 0-255 means total 256 group default is 0 and in one group max can be 16 router.
8. What is HSRP Coup message ?
1. Coup message is generated by this new highest priority router