Mod6 Redundancy

Improving Availability in Multilayer Switched Networks

Jan 2003

© 2003, Cisco Systems, Inc. All rights reserved.

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Multilayer Network Design Access

Distribution

Backbone

Core

Building Block Additions

Server Farm

WAN Jan 2003

© 2003, Cisco Systems, Inc. All rights reserved.

Internet

PSTN 2

Multi-VLAN Load Balancing Methods Layer-2 Mode Load Balancing

Layer-3 Mode Load Balancing

HSRP 1A HSRP 2s

HSRP 1s HSRP 2A

VLAN Trunk A&B VL AN B d Tr lo V ck LA un k VL N A& AN A B B Fw

B A& B k A un LAN AN r T V L N d kV A w F loc VL B

VLAN A and B

Jan 2003

© 2003, Cisco Systems, Inc. All rights reserved.

Fo

rw

ar d

VL AN VL

AN

Tr un A

k

A&

B

AN L V

u Tr

nk

Fo

B A&

rw

d ar

V

N LA

B

VLAN A and B

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First Hop Redundancy Schemes

• Hot Standby Router Protocol (HSRP) Cisco informational RFC 2281 ( March 1998)

• Virtual Router Redundancy Protocol (VRRP) IETF Standard RFC 2338 (April 1998)

• Gateway Load Balancing Protocol (GLBP) Cisco designed, load sharing, patent pending

Jan 2003

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HSRP • A group of routers function as one virtual router by sharing ONE virtual IP address and ONE virtual MAC address • One (Active) router performs packet forwarding for local hosts • The rest of the routers provide “hot standby” in case the active router fails • Standby routers stay idle as far as packet forwarding from the client side is concerned Jan 2003

© 2003, Cisco Systems, Inc. All rights reserved.

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First Hop Redundancy with HSRP R1- Active, forwarding traffic; R2, R3 - hot standby, idle HSRP ACTIVE IP: 10.0.0.254 MAC: 0000.0c12.3456 vIP: 10.0.0.10 vMAC: 0000.0c07ac00

HSRP STANDBY IP: 10.0.0.253 MAC: 0000.0C78.9abc vIP: vMAC:

R1

Clients IP: MAC: GW: ARP: Jan 2003

HSRP LISTEN IP: 10.0.0.252 MAC: 0000.0cde.f123 vIP: vMAC:

R2

CL1

10.0.0.1 aaaa.aaaa.aa01 10.0.0.10 0000.0c07.ac00

R3

CL2

IP: MAC: GW: ARP:

© 2003, Cisco Systems, Inc. All rights reserved.

10.0.0.2 aaaa.aaaa.aa02 10.0.0.10 0000.0c07.ac00

Gateway routers

CL3

IP: MAC: GW: ARP:

10.0.0.3 aaaa.aaaa.aa03 10.0.0.10 0000.0c07.ac00 6

VRRP • Very similar to HSRP • A group of routers function as one virtual router by sharing ONE virtual IP address and ONE virtual MAC address • One (master) router performs packet forwarding for local hosts • The rest of the routers act as “back up” in case the master router fails • Backup routers stay idle as far as packet forwarding from the client side is concerned Jan 2003

© 2003, Cisco Systems, Inc. All rights reserved.

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First Hop Redundancy with VRRP R1- Master, forwarding traffic; R2, R3 - backup VRRP ACTIVE IP: 10.0.0.254 MAC: 0000.0c12.3456 vIP: 10.0.0.10 vMAC: 0000.5e00.0100

VRRP BACKUP IP: 10.0.0.253 MAC: 0000.0C78.9abc vIP: vMAC:

R1

Clients IP: MAC: GW: ARP: Jan 2003

VRRP BACKUP IP: 10.0.0.252 MAC: 0000.0cde.f123 vIP: vMAC:

R2

CL1

10.0.0.1 aaaa.aaaa.aa01 10.0.0.10 0000.5e00.0100

R3

CL2

IP: MAC: GW: ARP:

© 2003, Cisco Systems, Inc. All rights reserved.

10.0.0.2 aaaa.aaaa.aa02 10.0.0.10 0000.5e00.0100

Gateway routers

CL3

IP: MAC: GW: ARP:

10.0.0.3 aaaa.aaaa.aa03 10.0.0.10 0000.5e00.0100 8

GLBP Defined

• A group of routers function as one virtual router by sharing ONE virtual IP address but using Multiple virtual MAC addresses for traffic forwarding • Provides uplink load-balancing as well as first hop fail-over • IP Leadership feature

Jan 2003

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GLBP Requirements • Allow traffic from a single common subnet to go through multiple redundant gateways using a single virtual IP address • Provide upstream load-balancing by utilizing the redundant up-links simultaneously • Eliminate the need to create multiple vLANs or manually divide clients for multiple gateway IP address assignment • Preserve the same level of first-hop failure recovery capability as provided by HSRP

Jan 2003

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First Hop Redundancy with GLBP R1- AVG; R1, R2, R3 all forward traffic GLBP AVG/AVF,SVF IP: 10.0.0.254 MAC: 0000.0c12.3456 vIP: 10.0.0.10 vMAC: 0007.b400.0101

GLBP AVF,SVF IP: 10.0.0.253 MAC: 0000.0C78.9abc vIP: 10.0.0.10 vMAC: 0007.b400.0102

R1

Clients IP: MAC: GW: ARP: Jan 2003

GLBP AVF,SVF IP: 10.0.0.252 MAC: 0000.0cde.f123 vIP: 10.0.0.10 vMAC: 0007.b400.0103

R2

CL1

10.0.0.1 aaaa.aaaa.aa01 10.0.0.10 0007.B400.0101

R3

CL2

IP: MAC: GW: ARP:

© 2003, Cisco Systems, Inc. All rights reserved.

10.0.0.2 aaaa.aaaa.aa02 10.0.0.10 0007.B400.0102

Gateway routers

CL3

IP: MAC: GW: ARP:

10.0.0.3 aaaa.aaaa.aa03 10.0.0.10 0007.B400.0103 11

Campus Access Layer Design GLBP balances traffic across both layer-3 switches

Better utilization of resources and uplinks

Campus Network

Layer-3 switches at distribution layer

10.88.49.10 10.88.50.10 vIP address

vMAC A vMAC C

vMAC B vMAC D

Layer-2 switches at access layer A GW= 10.88.49.10

Jan 2003

B

A

B

© 2003, Cisco Systems, Inc. All rights reserved.

C

D

C

D

GW= 10.88.50.10

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Service Provider Edge High Availability for Remote Office GLBP balances traffic across both routers

Better utilization of resources and uplinks

SP Network

Redundant CPE routers

10.88.49.10 10.88.50.10 vIP address

vMAC A vMAC C

vMAC B vMAC D

Layer-2 switches at access layer A GW= 10.88.49.10 Jan 2003

B

A

B

© 2003, Cisco Systems, Inc. All rights reserved.

C

D

C

D GW= 10.88.50.10 13

Server Farm Example L2 Dual-homed servers for port and switch redundancy

Layer-2 switches at access layer

Layer-3 switches at distribution layer

Some application but SLB more appropriate Jan 2003

10.88.49.10 vIP address

Campus Network

© 2003, Cisco Systems, Inc. All rights reserved.

GLBP balances traffic across both layer-3 switches Better utilization of resources and uplinks

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SLB – Server Load Balancing • SLB Presents a Virtual Address and Load Balances the Traffic Across Multiple Servers • Virtual Server: Represents an instance of a server farm • Real Server: An individual server within the farm

Jan 2003

© 2003, Cisco Systems, Inc. All rights reserved.

Virtual IP 192.168.1.200

192.168.1.1 80

192.168.1.2 80

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SLB Benefits • High performance is achieved by distributing client requests across a cluster of servers. • Administration of server applications is easier Clients know only about virtual servers No administration is required for real server changes Maintenance with continuous availability is achieved by allowing physical (real) servers to be transparently placed in or out of service

• Security of the real server is provided because its address is never announced to the external network Users are familiar only with the virtual IP address Filtering of unwanted traffic can be based on both IP address and IP port numbers Jan 2003

© 2003, Cisco Systems, Inc. All rights reserved.

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MSFC2 High Availability Features

• Provides multilayer switching and routing services between switched VLANs • Dependent on Supervisor Supervisor reset or failure will reset the MSFC2

• Operates in Dual Router Mode (DRM) or Single Router Mode (SRM)

Jan 2003

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Dual Router Mode (DRM) • Both MSFCs online • Each MSFC independently builds an accurate picture of the Layer 3 network • The failover mechanism between MSFCs in DRM is the HSRP • MSFCs maintain nearly identical configurations • First online is ‘designated router’, second is ‘nondesignated router’ Designated router programs the Layer 3 entries in the PFC2s Cisco Express Forwarding (CEF) table

Jan 2003

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MSFC Config Sync • Startup and running configurations between the designated (primary) and nondesignated (secondary) MSFCs are synchronized • The following commands enable MSFC config-sync: MSFC-Sup-15 (config)# redundancy MSFC-Sup-15 (config-r)# high-availability MSFC-Sup-15 (config-r-ha)# config-sync • Configuration of the nondesignated MSFC is accomplished through the use of the alt keyword MSFC-Sup-15 (config-if)# ip address a.b.c.1 x.x.x.0 alt ip address a.b.c.2 x.x.x.0 MSFC-Sup-15 (config-if)# standby 10 priority 100 alt standby 10 priority 50 Jan 2003

© 2003, Cisco Systems, Inc. All rights reserved.

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Sample DRM Configuration DRM hostname DRM ! redundancy high-availability config-sync ! interface Vlan20 ip address 10.20.1.3 255.255.255.0 alt ip address 10.20.1.2 255.255.255.0 standby ip 10.30.1.4 standby priority 100 alt standby priority 50 no ip redirects ! interface Vlan30 ip address 10.30.1.3 255.255.255.0 alt ip address 10.30.1.2 255.255.255.0 standby ip 10.30.1.4 standby priority 100 alt standby priority 50 no ip redirects ! end Jan 2003

© 2003, Cisco Systems, Inc. All rights reserved.

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DRM Challenges • Each MSFC must have a unique IP address for each VLAN interface • At least one router (the other MSFC) on each VLAN receives non-RPF traffic when multicast is used • Requirement for exact configuration parameters on both MSFCs complicates matters

Jan 2003

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SRM – Single Router Mode • Single Router Mode (SRM) addresses the drawbacks of the previous HSRP based redundancy scheme • Only the designated router (MSFC) is visible to the network at any given time • Non-designated router is booted up completely and participates in configuration synchronization, which is automatically enabled when entering SRM • Non-designated router interfaces are kept in a "line down" state and are not visible to the network Jan 2003

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SRM Requirements • Both MSFCs must run the same IOS image • High availability needs to be configured on the SUP MSFC-Sup-15 (config)# redundancy MSFC-Sup-15 (config-r)# high-availability MSFC-Sup-15 (config-r-ha)# single-router-mode

• Routing protocol processes are also created on the non-designated router, but dormant

Jan 2003

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Sample SRM Configuration SRM hostname SRM ! redundancy high-availability single-router-mode ! interface Vlan20 ip address 10.20.1.3 255.255.255.0 no ip redirects ! interface Vlan30 ip address 10.30.1.3 255.255.255.0 no ip redirects ! end Jan 2003

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Verify SRM Configuration • sh redundancy command can be used to verify that SRM is enabled: SRM# show redundancy Designated Router: 1 Non-designated Router: 2 Redundancy Status: designated Config Sync AdminStatus : enabled Config Sync RuntimeStatus: enabled Single Router Mode AdminStatus : enabled Single Router Mode RuntimeStatus: enabled Single Router Mode transition timer : 120 seconds

• Transition timer is used to ensure routing protocol convergence prior to PFC updates Jan 2003

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Presentation_ID Jan 2003

© 2001, 2003, Cisco Systems, Inc. All rights reserved.

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