20 - Implementing HSRP for First Hop Routing Flashcards
What are 3 types of First Hop Redundancy Protocols (FHRP)?
HSRP, VRRP, and GLBP
In addition to the minimum single command needed to implement HSRP, what other commands can be used?
* standby ver 2 * standby 1 ip 10.1.1.1 * standby 1 priority 110 * standby 1 name whatever
What is the default priority in HSRP?
100
In HSRP if the two routers are brought up at the same time who wins the election as active router?
The router with the highest priority
What ‘show’ cmd tells you which router is active?
show standby brief’
What does ‘standby preempt’ do?
If an HSRP router comes up and finds another HSRP router that is active it checks priority. If it 1) has a higher priority and 2) is configured with ‘standby preempt’ it will take over the active role
What are the two versions of HSRP?
version 1 and version 2
Do two routers in an HSRP group have to run the same version?
yes.
What will happen if two HSRP routers are using two different HSRP versions?
They won’t recognize each other.
What are the 6 differences between HSRP version 1 and version 2?
- ver 2 supports IPv6
- ver 2 supports faster Hello timer
- ver 2 supports up to 4095 group numbers
- ver 2 configures its vmac address differently
- ver 2 uses different multicast address
- ver 2 supports unique identifier for each HSRP router
What is the difference between HSRP ver 1 vmac and ver 2 vmac?
ver 1 vmac the last two hex digits are variable, ver 2 the last 3 hex digits are variable
What version of HSRP uses a vmac address of 0000.0C07.Acxx ?
version 1
What version of HSRP uses a vmac address of 0000.0C9F.Fxxx ?
version 2
For 2 routers in an HSRP group, what config parameters must match?
- version number
- same standby group #
- same virtual IP
- virtual IP must be in same subnet as IP address
- same VLAN
In addition to checking the parameters that must match what other troubleshooting steps should you do?
- make sure no ACL is filtering UDP port 1985
- ver 1 sends to 224.0.0.2
- ver 2 sends to 224.0.0.102
What would happen if the 2 HSRP routers had different virtual Ips configured?
* HSRP would not go active * virtual IP changes based on whichever router is active
What would happen if the 2 HSRP routers were using different versions?
They would become active but a duplicate IP address would be detected
What would happen if the 2 HSRP routers had a group mismatch?
They would become active but a duplicate IP address would be detected
HSRP, at a minimum, needs only a single command to work. What is that command?
standby 1 ip 172.21.2.1
What 7 items are shown by ‘show standby brief”
- Interface
- Group
- Priority
- State
- Active
- Standby
- Virtual IP
What are HSRP default Hello and Hold timers?
- Hello is 3 sec
- Hold is 10 sec
What are the rules that determine which HSRP point is active?
- if the local router doesn’t see any other HSRP routers it becomes active
- Whichever router has the highest priority wins the election
- If a router comes up, sees and already active HSRP even if the other router has higher priority it will go into standy unless….
- the local router is configured to Preempt
What ‘show’ command should allow you to back-engineer the HSRP configuration?
show standby
What commands are used to track the line protocol of an interface?
- track 1 interface Serial0/0/0 line-protocol
Then in HSRP config add:
- int gig0/0
- standby 1 track 1 decrement 50
What are the 6 states that HSRP can be in?
- Init - first starting
- Learn - no virtual IP address, no Hellos
- Listen - knows virtual IP, no Hellos but listening for them
- Speak - Has virtual IP, participates in election, is sending Hellos
- Standby - Not the active HSRP point
- Active - Is the Active HSRP router
