Nortel Networks WEB OS 212777 - Manual (Page 266)

Web OS 10.0 Application Guide
266 n Chapter 11: High Availability
212777-A, February 2002
To implement this example, configure the switches as follows:
1. Configure the appropriate Layer 2 and Layer 3 parameters on both switches.
This configuration includes any required VLANs, IP interfaces, default gateways, and so on. If
IP interfaces are configured, none of them should use the VIP address described in Step 4.
2. Define all filters required for your network configuration.
Filters may be configured on one switch and synchronized with the settings on the other switch
(see
Step 5 , below).
3. Configure all required SLB parameters on one of the switches.
For the purposes of this example, assume that Web switch 1 (see Figure 11-9 on page 265 ) is
configured in this step. Required Layer 4 parameters include a VIP = 205.178.13.226 and one
real server group with two real servers, RIP = 205.178.13.101 and RIP = 205.178.13.102.
RIP = 205.178.13.103 should be configured as a backup server to RIP = 205.178.13.101.
RIP = 205.178.13.104 should be configured as a backup server to RIP = 205.178.13.102.
N OTE – In this configuration, each server’s backup is attached to the other switch. This ensures
that operation will continue if all of the servers attached to a switch fail.
4. Configure the VRRP parameters on the switch.
Configure VRID = 2, VIP address = 205.178.13.226, and priority. Be sure to enable sharing.
5. Synchronize the SLB and VRRP configurations by pushing the configuration from Web
switch 1 to Web switch 2.
Use the /oper/slb/sync command.
6. Reverse the roles of the real servers and their backups in Web switch 2’s configuration.
Configure RIP = 205.178.13.103 and RIP= 205.178.13.104 as the real servers
Configure RIP = 205.178.13.101 and RIP = 205.178.13.102 as their backups, respectively.
In this configuration, if a link between a switch and a server fails, the server will fail health
checks and its backup (attached to the other switch) will be brought online. If a link between a
switch and its Internet router fails, the protocol used to distribute traffic between the routers
(for example, OSPF) will reroute traffic to the other router. Since all traffic now enters the vir-
tual server router on one switch, that switch will process all incoming connections.
If an entire master switch fails, the backup will detect this failure because it will stop receiving
advertisements. The backup will assume the master’s responsibility of responding to ARP
requests and issuing advertisements.
Be cautious before setting the maximum connections ( maxconn ) metric in this configuration.
The maxcon number is not shared between switches. Therefore, if a server is used for normal
operation by one switch and is activated simultaneously as a backup by the other switch, the
total number of possible connections to that server will be the sum of the maximum connection
limits defined for it on both switches.