Border Gateway Protocol (BGP) plays a pivotal role in the networking world, governing how routers share information about the paths data can take as it travels across the internet. Over the years, techniques to improve the efficiency of BGP have been adopted, but one of the most notable changes in recent times has been the transition from peer-groups to update-groups.
A Closer Look at Peer-Groups
In the traditional BGP setup, network administrators often used peer-groups to manage multiple BGP neighbors with the same outbound policies. Peer-groups allowed BGP configurations to be bundled together and applied to several routers at once.
Here’s an example of how a typical peer-group configuration would look like:
Router# show run | s bgp
router bgp 65000
neighbor PEER_GROUP peer-group
neighbor PEER_GROUP remote-as 65001
neighbor 192.0.2.1 peer-group PEER_GROUP
neighbor 192.0.2.2 peer-group PEER_GROUP
!
address-family ipv4
neighbor PEER_GROUP route-map BGP_OUTBOUND_POLICY out
exit-address-family
!
ip access-list standard BGP_OUTBOUND_FILTER
permit 203.0.113.0 0.0.0.255
!
route-map BGP_OUTBOUND_POLICY permit 10
match ip address BGP_OUTBOUND_FILTER
set metric 100
Transition to Update-Groups
However, Cisco has moved away from using peer-groups, rendering them obsolete. Now, they have been replaced by update-groups. The significant advantage is that update-groups are formed automatically by the router when it detects that multiple neighbors have the same outbound policies, significantly simplifying the configuration process.
Here’s how the new-style configuration without peer-groups would look like:
Router# show run | s bgp
router bgp 65000
neighbor 192.0.2.1 remote-as 65001
neighbor 192.0.2.2 remote-as 65002
!
address-family ipv4
neighbor 192.0.2.1 route-map BGP_OUTBOUND_POLICY out
neighbor 192.0.2.2 route-map BGP_OUTBOUND_POLICY out
exit-address-family
!
ip access-list standard BGP_OUTBOUND_FILTER
permit 203.0.113.0 0.0.0.255
!
route-map BGP_OUTBOUND_POLICY permit 10
match ip address BGP_OUTBOUND_FILTER
set metric 100
Some reasons why update-groups are preferred over peer-groups
1. Efficiency in Update Generation: Update groups handle the generation of updates more efficiently because they send a single update to all members of the group. In contrast, peer groups might require separate updates for each peer.
2. Reduced CPU Utilization: Update groups help to reduce CPU utilization by reducing the need for individual update generation.
3. Network Scalability: Update groups can scale better as the network grows. As more peers are added, the efficiency of update generation and distribution improves, unlike peer groups.
4. BGP Convergence: Update groups can improve BGP convergence times by streamlining the update process. The calculation of updates is performed just once for neighbors that share an identical outbound policy.
5. Better Memory Usage: Update groups use memory more efficiently. They only need to store one copy of an update, even if it is being sent to multiple peers.
6. Consistency in Routing Decisions: Update groups enforce more consistent routing decisions across the network because all peers in an update group receive the same updates.
7. Compatibility: Update groups are generally compatible with most types of peers and sessions.
8. Ease of Configuration: While both peer groups and update groups aim to simplify BGP configuration, the internal processing efficiency of update groups might make them a preferred choice.
9. Improved Performance: Update groups generally perform better than peer groups in terms of speed and efficiency of route propagation.
10. Adaptability: Update groups are designed to adapt better to modern, large-scale networks where numerous BGP sessions may exist.
Conclusion
The transition from peer-groups to update-groups has provided a more streamlined configuration experience for network administrators. By automatically allowing the router to group neighbors based on the same policies, the system offers greater intuitiveness and less room for confusion.
While the change might seem daunting at first, it is a step forward for BGP efficiency in practice. The outcome remains the same, improved updates, but the process to get there has become significantly more straightforward.
So, embrace the new update-groups, because they are here to stay!