BGP max prefix

• Router có bộ nhớ RAM và khả năng CPU xử lý có hạn nên chỉ xử lý được một lượng prefix nhận được nhất định. Max-prefix là feature nhằm hạn chế lượng prefix router nhận được.

• Có 2 option config:

 <1-100>       Threshold value (%) at which to generate a warning msg

  restart       Restart bgp connection after limit is exceeded

  warning-only  Only give warning message when limit is exceeded

  <cr>

• <1-100> lượng max prefix
• Restart: sau khi router nhận lượng prefix > max-prefix => neighbor BGP chuyển sang trạng thái IDLE. Restart là time để BGP try neighbor

• Warning-only: router sẽ  sinh ra log và lượng pre-fix vẫn được nhận xử lý

R1: interface Loopback0  ip address 1.1.1.1 255.255.255.0 ! interface Loopback1  ip address 11.11.11.11 255.255.255.0 ! interface Loopback2  ip address 111.111.111.111 255.255.255.0 ! interface FastEthernet0/0  ip address 10.1.12.1 255.255.255.0  ! router bgp 1   bgp router-id 1.1.1.1  bgp log-neighbor-changes  network 1.1.1.0 mask 255.255.255.0  network 11.11.11.0 mask 255.255.255.0  neighbor 10.1.12.2 remote-as 1  ----------------------------------------------------------  network 111.111.111.0 mask 255.255.255.0  3 prefix advertise to IOS-XR

IOS-XR interface GigabitEthernet0/0/0/2  ipv4 address 10.1.12.2 255.255.255.0 router bgp 1  bgp router-id 2.2.2.2  address-family ipv4 unicast  !  neighbor 10.1.12.1   remote-as 1   address-family ipv4 unicast    maximum-prefix 2 1 restart 1 ! // IOS-XR can treat only 2 prefix. If it over, neigbor go down and syslog RP/0/0/CPU0:ios#show bgp ipv4 unicast neighbors 10.1.12.1 | i prefixes Wed Mar 11 10:04:01.784 UTC   2 accepted prefixes, 2 are bestpaths   Cumulative no. of prefixes denied: 0.   Maximum prefixes allowed 2   Last reset 00:24:35, due to Peer exceeding maximum prefix limit (CEASE notification sent - maximum number of prefixes reached)   Error Code: maximum number of prefixes reached

RP/0/0/CPU0:ios#RP/0/0/CPU0:Mar 11 09:39:05.287 : bgp[1047]: %ROUTING-BGP-5-MAXPFX : No. of IPv4 Unicast prefixes received from 10.1.12.1 has reached 2, max 2

RP/0/0/CPU0:Mar 11 09:39:26.735 : bgp[1047]: %ROUTING-BGP-4-MAXPFXEXCEED : No. of IPv4 Unicast prefixes received from 10.1.12.1: 3 exceed limit 2

RP/0/0/CPU0:Mar 11 09:39:26.735 : bgp[1047]: %ROUTING-BGP-5-ADJCHANGE : neighbor 10.1.12.1 Down - Peer exceeding maximum prefix limit (CEASE notification sent - maximum number of prefixes reached) (VRF: default) (AS: 1