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Chapter 8 Configuring HSRP for Fault Tolerant Routing

Chapter 8 Configuring HSRP for Fault Tolerant Routing. Objectives. Upon completion of this chapter, you will be able to perform the following tasks: Identify the virtual router for a given set of switch block devices Configure HSRP on switch block devices to ensure continual interVLAN routing

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Chapter 8 Configuring HSRP for Fault Tolerant Routing

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  1. Chapter 8 Configuring HSRP for Fault Tolerant Routing

  2. Objectives • Upon completion of this chapter, you will be able to perform the following tasks: • Identify the virtual router for a given set of switch block devices • Configure HSRP on switch block devices to ensure continual interVLAN routing • Maintain graceful packet forwarding by changing the active and standby HSRP router roles • Ensure the role of the active router by assigning a preempt status.

  3. Configuring HSRP for Fault- Tolerant Routing • In this chapter, we discuss the following topics: • HSRP overview • HSRP operations • Configuring HSRP

  4. Configuring HSRP for Fault Tolerant Routing • In this section we discuss the following topics: • HSRP Overview • Routing Problems • Solution: HSRP • Multiple HSRP Groups • HSRP Operations • Configuring HSRP

  5. Problem: Using Default Gateways I need to get to File Server A but my default gateway is down. I can route packetsto File server A. Router 1 172.16.10.820010.f6b3.d000 Router 2 172.16.10.1690010.0b79.5800 Subnet A 172.16.50.0 Subnet B 172.16.51.0 Core File Server A

  6. Problem: Using Proxy ARP I need to get to 172.16.3.127 Use MAC address 0010.0b79.5800 Router 1 172.16.10.820010.f6b3.d000 Router 2 172.16.10.1690010.0b79.5800 Subnet B 172.16.51.0 Subnet A 172.16.50.0 Core File Server A172.16.3.127

  7. Problem: Using RIP I have a path to 172.16.3.127 I can get to File Server Aby 172.16.10.82 in 1 hop and by 172.16.10.169 in 2 hops. I have a path to 172.16.3.127 Router 1 172.16.10.820010.f6b3.d000 Router 2 172.16.10.1690010.0b79.5800 Subnet B 172.16.51.0 Subnet A 172.16.50.0 Core File Server A172.16.3.127

  8. Problem: Using Using RIP (cont.) 172.16.10.82 is no longeravailable. I can still reach File Server A by 172.16.10.169 in 2 hops. I still have a pathto 172.16.3.127 Router 1 172.16.10.820010.f6b3.d000 Router 2 172.16.10.1690010.0b79.5800 Subnet A 172.16.50.0 Subnet B 172.16.51.0 Core File Server A172.16.3.127

  9. Problem: Using IRDP I haven’t heard a hello message from my preferred router. I will send packets to my alternate router. Preferred Router 172.16.10.820010.f6b3.d000 Alternate Router 172.16.10.1690010.0b79.5800 Core File Server A172.16.3.127

  10. Solution: Hot Standby Routing Protocol HSRP Group Core • HSRP defines a set of routers working together to represent one virtual fault-tolerant router

  11. Solution: Hot Standby Routing Protocol (cont.) Active Router Core • Packets are still routed even when the active router fails

  12. HSRP Group Members HSRP Group Active Router Standby Router Virtual Router • HSRP standby groups consist of multiple routers performing specific roles

  13. HSRP Groups Active Router for Group 1 Standby Router for Group 2 Router A Group 2 Network 172.16.10.0 Vlan 10 Group 1 Router B Standby Router for Group 1 Active Router for Group 2 • Routers can belong to multiple groups on the same subnet in a VLAN

  14. Addressing HSRP Groups across ISL Links VLAN20 VLAN10 VLAN20 VLAN10 ISL Link Carrying Both VLAN 10 and 20 Traffic ISL Link Ccarrying Both VLAN 10 and 20 Traffic ISL Link Carrying Both VLAN 10 and 20 Traffic 172.16.10.110 Virtual Router for VLAN10 172.16.20.120 Virtual Router for VLAN20 Router B Router A interface FastEthernet 1/1.10 encapsulation isl 10 ip address 172.16.10.3 255.255.255.0 standby 1 ip 172.16.10.110 standby 1 priority 50 interface FastEthernet 1/1.20 encapsulation isl 20 ip address 172.16.20.3 255.255.255.0 standby 2 ip 172.16.20.120 standby 2 priority 105 standby 2 preempt interface FastEthernet 1/1.10 encapsulation isl 10 ip address 172.16.10.2 255.255.255.0 standby 1 ip 172.16.10.110 standby 1 priority 105 standby 1 preempt interface FastEthernet 1/1.20 encapsulation isl 20 ip address 172.16.20.2 255.255.255.0 standby 2 ip 172.16.20.120 standby 2 priority 50

  15. Group 1 Group 2 Vlan 10 Network 172.16.10.0 Network 172.16.20.0 Vlan 20 Group 3 Group 4 Multiple HSRP Groups • Routers can belong to multiple groups in multiple VLANs

  16. Configuring HSRP for Fault- Tolerant Routing • In this section we discuss the following topics: • HSRP Overview • HSRP Operations • Active and standby router roles • Interactions between active and standby routers • HSRP states • Configuring connectivity within the switch block

  17. Use MAC address 0000.0c07.ac0a Designating an Active Router I need to get to 172.16.3.127 Virtual Router 172.16.10.110 0000.0c07.ac0a Router B Priority 100 172.16.10.1690010.0b79.5800 Router A Priority 200 172.16.10.820010.f6b3.d000 Core File Server A172.16.3.127 • The router with the highest HSRP priority becomes the active router • The active router responds to ARP requests with the MAC address of the virtual router

  18. Locating the Virtual Router MAC Address HSRP Group 47 Router#show ip arp 172.16.10.82 172.16.10.169 172.16.10.110 Protocol Address Age (min) Hardware Addr Type Interface Internet 172.16.10.82 - 0010.f6b3.d000 ARPA Vlan10 Internet 172.16.10.169 - 0010.0b79.5800 ARPA Vlan10 Internet 172.16.10.110 0000.0c07.ac0a ARPA Vlan10 Vendor Code HSRP Group Number HSRP Well-Known Virtual MAC Address

  19. Active and Secondary Router Interaction HSRP Group 47 Active Router172.16.10.82 Router in Standby State172.16.10.169 Virtual Router172.16.10.110 Hello Message 1d23h : SB47:Vlan10 Hello out 172.16.10.82 Active pri 200 hel 3 hol 10 ip 172.16.10.110 • The active router broadcasts periodic hello messages

  20. Active and Secondary Router Interaction (cont.) I haven’t heard a Hello Message from the active router. I will assume the active router role. HSRP Group 47 Virtual Router172.16.10.110 Router in Active State172.16.10.169 Hello Message 1d23h: SB47:Vlan10 Hello out 172.16.10.169 Active pri 100 hel 3 hol 10 ip 172.16.10.110

  21. HSRP Message Format 1 Octet 1 Octet 1 Octet 1 Octet Version Op Code State HelloTime Holdtime Priority Group Reserved Authentication Data Authentication Data Virtual IP Address • HSRP messages utilize the data portion of a UDP datagram

  22. Selecting Active and Standby Routers 3w1d:%STANDBY-6-STATECHANGE: Standby: 0: Vlan10 state Init -> Listen 3w1d:%STANDBY-6-STATECHANGE: Standby: 0: Vlan10 state Listen -> Speak 3w1d:SB47:Vlan10 Hello out172.16.10.82 Speak pri150 hel 3 hol 10 ip 172.16.10.110 3w1d:%STANDBY-6-STATECHANGE: Standby: 47: Vlan10 state Speak -> Standby 3w1d:%STANDBY-6-STATECHANGE: Standby: 47: Vlan10 state Standby -> Active 3w1d:SB: Vlan10 Adding 0000.0c07.ac0a to address filter

  23. Selecting Active and Standby Routers 3w1d:%STANDBY-6-STATECHANGE: Standby: 0: Vlan10 state Init -> Listen 3w1d:%STANDBY-6-STATECHANGE: Standby: 0: Vlan10 state Listen -> Speak 3w1d:SB47:Vlan10 Hello out172.16.10.82 Speak pri150 hel 3 hol 10 ip 172.16.10.110 3w1d:%STANDBY-6-STATECHANGE: Standby: 47: Vlan10 state Speak -> Standby 3w1d:%STANDBY-6-STATECHANGE: Standby: 47: Vlan10 state Standby -> Active 3w1d:SB: Vlan10 Adding 0000.0c07.ac0a to address filter • Each router in the group participates in the protocol by implementing a simple state machine. • All routers begin in the Initial state.

  24. HSRP Initial State Virtual Router 172.16.10.110 Router in Initial State 172.16.10.82 Router in Initial State 172.16.10.169 • No HSRP is running

  25. HSRP Learn State Virtual Router 172.16.10.110 Active Router 172.16.10.82 Router in Learn State 172.16.10.169 • Have not received a hello message from the active router • Do not know the virtual router IP address

  26. HSRP Listen State Virtual Router 172.16.10.110 Active Router 172.16.10.82 Router in Listen State 172.16.10.169 1d23h: SB47:Vlan10 Hello out 172.16.10.82 Active pri 200 hel 3 hol 10 ip 172.16.10.110 • Neither the active nor the standby router • Receives hello message • Knows the virtual router IP address

  27. HSRP Speak State Virtual Router 172.16.10.110 Active Router 172.16.10.82 Router in Speak State 172.16.10.169 1d23h: SB47: Vlan10 Hello out 172.16.10.169 Speak pri 100 hel 3 hol 10 ip 172.16.10.110 • Sends periodic hello messages • Participates in the election of the active and standby router • Knows the virtual router IP address

  28. HSRP Standby State Virtual Router 172.16.10.110 Active Router 172.16.10.82 Router in Standby State 172.16.10.169 1d23h: SB47:Vlan10 Hello out 172.16.10.169 Standby pri 100 hel 3 hol 10 ip 172.16.10.110 • Candidate for active router • Sends hello message • Knows the virtual router IP address

  29. HSRP Active State Virtual Router 172.16.10.110 Active Router 172.16.10.82 Router in Standby State 172.16.10.169 1d23h: SB47:Vlan10 Hello out 172.16.10.82 Active pri 200 hel 3 hol 10 ip 172.16.10.110 • Assumes the active forwarding of packets for the virtual router • Sends hello message • Knows the virtual router IP address

  30. Configuring HSRP for Fault Tolerant Routing • In this chapter we discuss the following topics: • HSRP Overview • HSRP Operations • Configuring HSRP • Configuring the standby interface • Configuring the standby priority • Configuring the standby preempt • Configuring HSRP tracking • Using debug standby

  31. Configuring a HSRP Standby Interface Virtual Router IP Address Standby Group Number Router#show standby vlan 10 interface Vlan10 ip address 172.16.10.82 255.255.255.0 no ip redirects standby 47 ip 172.16.10.110 Router(config-if)#standby 47 ip 172.16.10.110 Virtual Router 172.16.10.110 172.16.10.82 • Enabling HSRP on a Cisco router interface automatically disables ICMP redirects

  32. Configuring HSRP Standby Priority Router#show standby vlan 10 interface Vlan10 ip address 172.16.10.82 255.255.255.0 no ip redirects standby 47 priority 150 standby 47 ip 172.16.10.110 Router(config-if)#standby 47 priority 150 Virtual Router 172.16.10.110 172.16.10.82 • The router in an HSRP group with the highest priority becomes the forwarding router

  33. Configuring HSRP Standby Preempt Router#show standby vlan 10 interface Vlan10 ip address 172.16.10.82 255.255.255.0 no ip redirects standby 47 priority 150 standby 47 preempt standby 47 ip 172.16.10.110 Router(config-if)#standby 47 preempt Virtual Router 172.16.10.110 172.16.10.82 • Preempt enables a router to resume the forwarding router role

  34. Configuring the Hello Message Timers • Building configuration... • Current configuration: • (text deleted) • ! • interface Vlan10 • ip address 172.16.10.82 255.255.255.0 • no ip redirects • standby 47 timers 5 15 • standby 47 ip 172.16.10.10 Router(config-if)#standby 47 timers 5 15 • The holdtime should be at least three times the value of the hellotime

  35. HSRP Interface Tracking Router A Active T1 Link S1 E0 T1 Link E0 S1 Router B Standby Headquarters Branch Office

  36. HSRP Interface Tracking Router A Active T1 Link E0 S1 T1 Link E0 S1 Router B Standby Headquarters Branch Office

  37. Configuring HSRP Tracking: External Router Amount to Decrement Priority Interface Tracked Interface Doing the Tracking Router#show standby interface E0 ip address 172.16.10.82 255.255.255.0 no ip redirects standby 47 ip 172.16.10.110 standby 47 track S1 50 Router(config)interface ethernet E0 Router(config-if)#standby 47 track S1 50 E0 S1 Virtual Router 172.16.10.110 172.16.10.82

  38. Configuring HSRP Tracking: Internal Router Vlan 45 Vlan 41 Amount to decrement priority Virtual Router 172.16.41.145 Interface tracked Interface doing the tracking interface Vlan41 ip address 172.16.41.144 255.255.255.0 no ip redirects standby 2 priority 150 standby 2 preempt standby 2 ip 172.16.41.145 standby 2 track vlan 45 50 Router(config)interface vlan 41 Router(config-if)#standby 2 track vlan 45 50

  39. Displaying the Standby Brief Status P indicates configured to preempt. Interface Grp Prio P State Active addr Standby addr Group addr V41 2 150 P Active local 172.16.41.3 172.16.41.145 V42 4 90 Standby 172.16.42.1 local 172.16.42.144 Router#show standby brief

  40. Using the debugstandby Command Router#debug standby 3w1d:%STANDBY-6-STATECHANGE: Standby: 0: Vlan10 state Init -> Listen 3w1d:%STANDBY-6-STATECHANGE: Standby: 0: Vlan10 state Listen -> Speak 3w1d:SB47:Vlan10 Hello out172.16.10.1 Speak pri150 hel 3 hol 10 ip 172.16.10.110 3w1d:SB47:Vlan10 Hello out172.16.10.1 Speak pri150 hel 3 hol 10 ip 172.16.10.110 3w1d:SB47:Vlan10 Hello out172.16.10.1 Speak pri150 hel 3 hol 10 ip 172.16.10.110 3w1d:SB47:Vlan10 Hello out172.16.10.1 Speak pri150 hel 3 hol 10 ip 172.16.10.110 3w1d:%STANDBY-6-STATECHANGE: Standby: 47: Vlan10 state Speak -> Standby 3w1d:%STANDBY-6-STATECHANGE: Standby: 47: Vlan10 state Standby -> Active 3w1d:SB: Vlan10 Adding 0000.0c07.ac0a to address filter 3w1d:SB: Vlan10 Adding 0000.0c07.ac0a to address filter 3w1d:SB47:Vlan10 Hello out172.16.10.1 Active pri150 hel 3 hol 10 ip 172.16.10.110 3w1d:SB47:Vlan10 Hello out172.16.10.1 Active pri150 hel 3 hol 10 ip 172.16.10.110 3w1d:SB47:Vlan10 Hello out172.16.10.1 Active pri150 hel 3 hol 10 ip 172.16.10.110

  41. Laboratory Exercise: Visual Objective Switch Block Ping VLAN A VLAN B Virtual Router Active Router Standby Router

  42. Summary • HSRP provides automatic router backup for end user devices. • Member router in an HSRP standby group present the illusion of a single virtual router to the hosts on the LAN. • HSRP standby groups must have one active and one standby router • Standby group routers communicated using multicast hello messages. • HSRP defines six states in which a router may exist. • Any protocol that informs a host of the router primary address must be disabled.

  43. Review • Discuss the basic tasks required to configure HSRP in the network. • Explain the purpose for active and standby routers and how these two entities interact. • Describe the six HSRP router states and the actions an HSRP router takes in each state.

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