1. Implementing Layer 3 High Availability
Configuring Layer 3 Redundancy with VRRP and GLBP
Implementing Layer 3 High Availability

2. HSRP vs. VRRP HSRP VRRP Cisco proprietary, 1994.
IETF 1998–2005, RFC 3768.
16 groups max.
255 groups max.
1 active, 1 standby, several candidates.
1 active, several backups.
Virtual IP is different from active and standby real IP addresses.
Virtual IP address can be the same as the real IP address of one of the group members.
Uses
Uses
Can track interfaces or objects.
Can track only objects.
Default timers: hello, 3 sec; hold time, 10 sec.
Default timers: hello, 1 sec; hold time, 3 sec.
Authentication supported.
Authentication no longer supported.

3. About VRRP

4. VRRP Operations Process

5. VRRP Configuration

6. About GLBP
Allows full use of resources on all devices without the administrative burden of creating multiple groups
Provides a single virtual IP address and multiple virtual MAC addresses
Routes traffic to single gateway distributed across routers
Provides automatic rerouting in the event of any failure

7. GLBP vs. HSRP HSRP GLBP Cisco proprietary, 1994.
16 groups max.
1024 groups max.
1 active, 1 standby, several candidates.
1 AVG, several AVFs; AVG load-balances traffic among AVFs and AVG.
Virtual IP is different from active and standby real IP addresses.
Virtual IP is different from AVG and AVF real IP addresses.
1 virtual MAC address for each group.
1 virtual MAC address per AVF or AVG in each group.
Uses
Uses
Can track interfaces or objects.
Can track only objects.
Default timers: hello, 3 sec; hold time, 10 sec.
Authentication supported.

8. GLBP Operations GLBP group members elect one AVG.
AVG assigns a virtual MAC address to each member of the group.
AVG replies to the ARP requests from clients with different virtual MAC addresses, thus achieving load balancing.
Each router becomes an AVF for frames that are addressed to that virtual MAC address.

9. GLBP Operation

10. GLBP Operation (Cont.)

11. GLBP Interface Tracking

12. GLBP Interface Tracking (Cont.)

13. GLBP Weights and Decrements

14. GLBP Configuration

15. GLBP and VLAN Spanning
Both distribution switches act as a default gateway.
Blocked uplink causes traffic to take a less-than-optimal path.

16. Summary
VRRP provides router redundancy in a manner similar to that of HSRP.
VRRP supports a master router and one or more backup routers.
VRRP is configured per interface.
GLBP provides router redundancy and load balancing.
GLBP balances traffic by allocating a virtual MAC address to each AVF.
The GLBP configuration steps are very similar to those of HSRP and VRRP.