Configuring a large number of similar BGP peers on a router and ensuring that the changes in your routing policy or BGP design are applied to all of them can be a management nightmare. BGP peer groups were the only scalability tool available on Cisco IOS until the IOS release 12.3T and they had significant limitations as they were also used as a performance improvement tool.

IOS releases 12.0S and 12.3T introduced peer templates, a scalable hierarchical way of configuring BGP session parameters and inbound/outbound policies. For example, to configure the session parameters for all your IBGP sessions, use the following session template:

router bgp 65001
 template peer-session IBGP
  remote-as 65001
  description IBGP peers
  password s3cr3t
  update-source Loopback0

After the session template has been configured, adding a new IBGP peer takes just a single configuration command (two if you want to add neighbor description):

router bgp 65001
 neighbor 10.0.1.2 inherit peer-session IBGP
 neighbor 10.0.1.2 description R2

Policy templates are similar to session templates, and contain neighbor parameters that influence processing of prefixes of an individual BGP address family (example: filtering of inbound updates).

Continuing the IBGP example, you might want to group route reflector clients in a policy template, and ensure the route reflector propagating all BGP communities to them:

router bgp 65001
 template peer-policy Internal
  route-reflector-client
  send-community both
 exit-peer-policy

After defining a policy template, you can apply it to multiple address families, for example:

router bgp 65001
 neighbor 10.0.1.2 inherit peer-session IBGP
 neighbor 10.0.1.2 description R2
!
 address-family ipv4
  neighbor 10.0.1.2 activate
  neighbor 10.0.1.2 inherit peer-policy Internal
 exit-address-family
 !
 address-family vpnv4
  neighbor 10.0.1.2 activate
  neighbor 10.0.1.2 inherit peer-policy Internal