Download CCNP 3 - IP Redundancy

Improving Availability in
Multilayer Switched Networks
Jan 2003
© 2003, Cisco Systems, Inc. All rights reserved.
1
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
VLAN A and B
Jan 2003
© 2003, Cisco Systems, Inc. All rights reserved.
VLAN A and B
3
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
© 2003, Cisco Systems, Inc. All rights reserved.
4
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.
5
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
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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.
7
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
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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
© 2003, Cisco Systems, Inc. All rights reserved.
9
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
© 2003, Cisco Systems, Inc. All rights reserved.
10
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
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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
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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
GLBP balances
traffic across both
layer-3 switches
Better utilization of
resources and
uplinks
Campus Network
© 2003, Cisco Systems, Inc. All rights reserved.
14
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.
16
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
© 2003, Cisco Systems, Inc. All rights reserved.
17
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
© 2003, Cisco Systems, Inc. All rights reserved.
18
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.
19
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.
20
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
© 2003, Cisco Systems, Inc. All rights reserved.
21
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
© 2003, Cisco Systems, Inc. All rights reserved.
22
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
© 2003, Cisco Systems, Inc. All rights reserved.
23
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
© 2003, Cisco Systems, Inc. All rights reserved.
24
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
© 2003, Cisco Systems, Inc. All rights reserved.
25
Presentation_ID
Jan 2003
© 2001,
2003, Cisco Systems, Inc. All rights reserved.
26