HSRP with Default Route Tracking (HSRP IP Route Tracking)

Rashmi Bhardwaj | Blog,Protocol,Routing & Switching
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HSRP + IP SLA tracking of remote IP” is a preferred failover approach wherein a remote IP is tracked to provide routing redundancy for routing IP traffic not dependent on the availability of any single.

Many a times network implementers/administrators will track Service provider DNS or some other globally available Global IP (via IP SLA monitor or RTR feature set using ICMP protocol ).

Some of tracked IPs I remember may be 8.8.8.8 or 4.2.2.2. Though I may not be referring to these IPs, however let’s not forget that tracked Global IPs may block ICMP ping to mitigate security threats like DOS/DDOS attacks. In this case, HSRP track protocol dependence on Global IP tracking may fail.

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To address this situation, we may use Default Route HSRP tracking.

Lab Scenario: HSRP with Default Route Tracking

Below is one lab scenario created to help understand the setup and requisite configuration of Default Route Tracking:

Note –

BGP timers have been manipulated in lab setup for faster convergence. This may be different from real life scenario.

R1

interface Loopback0ip address 1.1.1.1 255.255.255.0

!

interface FastEthernet0/0

ip address 192.168.123.1 255.255.255.0

!

ip route 0.0.0.0 0.0.0.0 192.168.123.4

R2

track 1 ip route 0.0.0.0 0.0.0.0 reachability >>>>>>> Track to verify whether default route is being learnt via BGP!

interface FastEthernet0/0

ip address 192.168.123.2 255.255.255.0

standby 1 ip 192.168.123.4

standby 1 priority 110

standby 1 preempt

standby 1 track 1 decrement 20>>>>>>> Decrement by 20 when tracked route is not available

!

interface FastEthernet0/1

ip address 192.168.24.2 255.255.255.0

!

router bgp 2

network 192.168.24.0

timers bgp 10 30 20 >>>> Timers updated for faster convergence

redistribute static metric 50

neighbor 192.168.24.4 remote-as 4

neighbor 192.168.24.4 soft-reconfiguration inbound

!

ip route 1.1.1.0 255.255.255.0 192.168.123.1

R3

interface FastEthernet0/0ip address 192.168.123.3 255.255.255.0

standby 1 ip 192.168.123.4

standby 1 preempt

!

interface FastEthernet0/1

ip address 192.168.34.3 255.255.255.0

!

router bgp 2

no synchronization

network 192.168.34.0

timers bgp 10 30 20

redistribute static metric 100

neighbor 192.168.34.4 remote-as 4

neighbor 192.168.34.4 soft-reconfiguration inbound

no auto-summary

!

ip route 1.1.1.0 255.255.255.0 192.168.123.1

R4

interface Loopback0ip address 4.4.4.4 255.255.255.0

!

interface FastEthernet0/0

ip address 192.168.24.4 255.255.255.0

!

interface FastEthernet0/1

ip address 192.168.34.4 255.255.255.0

!

router bgp 4

no synchronization

bgp log-neighbor-changes

network 0.0.0.0

network 4.4.4.0 mask 255.255.255.0

network 192.168.24.0

network 192.168.34.0

timers bgp 10 30 20

neighbor 192.168.24.2 remote-as 2

neighbor 192.168.24.2 soft-reconfiguration inbound

neighbor 192.168.34.3 remote-as 2

no auto-summary

!

ip route 0.0.0.0 0.0.0.0 Null0

Next , time to verify the configuration as below –

R2

R2#sh standby brief P indicates configured to preempt.

Interface   Grp   Prio P  State    Active         Standby         Virtual IP

Fa0/0         1        110  P  Active   local           192.168.123.3   192.168.123.4 >>>>>> Local Router is HSRP Master

R2#sh ip route 0.0.0.0

Routing entry for 0.0.0.0/0, supernet >>>>>>> Default Route entry in Routing table

Known via “bgp 2”, distance 20, metric 0, candidate default path

Tag 4, type external

Last update from 192.168.24.4 00:01:55 ago

Routing Descriptor Blocks:f

* 192.168.24.4, from 192.168.24.4, 00:01:55 ago

Route metric is 0, traffic share count is 1

AS Hops 1

Route tag 4

R2#show track 1

Track 1

IP route 0.0.0.0 0.0.0.0 reachability

Reachability is Up (BGP) >>>>>>>> Default Route is being learnt via BGP

10 changes, last change 00:01:56

First-hop interface is FastEthernet0/1

Tracked by:

HSRP FastEthernet0/0 1

R1

R1#traceroute 4.4.4.4 so lo0Type escape sequence to abort.

Tracing the route to 4.4.4.4

1 192.168.123.2 52 msec 56 msec 60 msec    >>>>>> Traceroute takes path via R2 (HSRP Active) path to reach R4 loopback

2 192.168.24.4 124 msec 120 msec 88 msec

Next, we will shut interface “Fa0/0” of  R4 as per below diagram:

R4 –

R4(config-if)#exitR4(config)#int fa0/0

R4(config-if)#shut

Below configuration shows that R2 is HSRP standby while R3 becomes HSRP active.

R2 –

R2#sh standby briefP indicates configured to preempt.

|

Interface   Grp Prio P State   Active         Standby         Virtual IP

Fa0/0       1   90   P Standby 192.168.123.3   local           192.168.123.4

 

R2#sh ip route 0.0.0.0

% Network not in table

R2#sh track 1

Track 1

IP route 0.0.0.0 0.0.0.0 reachability

Reachability is Down (no route)

9 changes, last change 00:01:14

First-hop interface is unknown

Tracked by:

HSRP FastEthernet0/0 1

R3 –

R3#sh standby brieP indicates configured to preempt.

Interface   Grp Prio P State   Active         Standby         Virtual IP

Fa0/0       1   100 P Active   local           192.168.123.2   192.168.123.4

Once R3 becomes the HSRP master (Active) , Traceroute from R1 Loopback to R4 Loopback should take path via R3 as below –

R1 –

R1#traceroute 4.4.4.4 so lo0Type escape sequence to abort.

Tracing the route to 4.4.4.4

1 192.168.123.3 64 msec 60 msec 60 msec

2 192.168.34.4 120 msec 116 msec 124 msec

Continue Reading:

Configuring IP SLA with HSRP

Multiple HSRP (MHSRP): Load Sharing FHRP

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