#ibgp

BGP

BGP is the protocol which is use for the routing between the different autonomous systems. BGP is a external gateway protocol that we are using nowadays. Below is an image that show you the place of BGP where it configure. The exact place is between the different autonomous systems and autonomous system basically is the collection of the routers. Here below there are the two different autonomous system 100 and 200 respectively and BGP is configure between autonomous systems. This protocol is the largest protocol that holds the multiple autonomous system for the communication.

Fig 1:Border Gateway Protocol

Autonomous system numbers are 16 bits and 2^16=65535 means that are numbers of autonomous systems we can choose from this numbers.

There are the public and private autonomous system numbers just like public and private addresses.

The range 1-64511 are globally unique/public AS numbers that are for the commercial purposes.

The range 64512-65535 are private autonomous system numbers.

When to use BGP ?

When autonomous system work as transit autonomous system and the other condition is when autonomous system connected to the multiple autonomous systems means when AS multi-homed.

When BGP is not appropriate ?

BGP is not appropriate if the autonomous system is single-home. When lack of resources there should no need to use BGP and the other main point is that when you are not familiar with the BGP how to use it and when you don't know about the BGP Route filtering and the processes of path selection.

BGP Features

BGP is also used internally means inside the autonomous system and is known as the IBGP.

Border Gateway Protocol is the Open Standard Protocol.

It is also known as the Path Vector Protocol

Configuring Load Balancing Among EBGP and IBGP Routes When CEs Are Dual-Homed

When a CE is dual homed to two PEs, if one PE is in the same AS as the remote PE, whereas the other PE is not in the same AS as the remote PE, you can configure EBGP and IBGP route load balancing.

Networking Requirements

As shown in Figure 1, CE1 and CE2 belong to the same VPN instance. CE1 accesses the network respectively through PE3 in AS 100 and PE2 in AS 200. That is, CE1 is dual-homed to PE3 and PE2. CE2 accesses the network through PE1 in AS 100.

The Inter-AS BGP/MPLS IP VPN is implemented using Option C so that load balancing can be implemented among EBGP and IBGP routes.

Figure 1 Networking diagram of configuring load balancing among EBGP and IBGP routes when CEs are dual-homed

Configuration Roadmap

The configuration roadmap is as follows:

Establish the MP-EBGP peer relationship between the PEs in different ASs. Since the PEs are generally not directly connected, you also need to configure the maximum hops between the PEs for them to set up an EBGP connection.

Configure a routing policy on the ASBR: Allocate MPLS labels to the the routes received by the PE in the local AS before advertising the route to the remote ASBR; allocate new MPLS labels to the labeled IPv4 routes advertised to the PE in the local AS.

Configure the PEs to exchange the labeled IPv4 routes with the ASBRs in the local AS.

Enable the capability of exchanging the labeled IPv4 routes between the local ASBR and the remote ASBR.

In the BGP-VPN instance view of PE1, enable load balancing among EBGP and IBGP routes to CE1.

Data Preparation

To complete the configuration, you need the following data.

MPLS LSR IDs of PEs and ASBRs

Names of VPN instance created on PEs, RD, and VPN target

Routing policies configured on ASBRs

Maximum number of EBGP and IBGP routes that perform load balancing

Procedure

Configure IGP on the MPLS backbone networks in AS 100 and AS 200 to implement interconnection between PEs and ASBRs in each MPLS backbone network.

Take OSPF as an example. The detailed configuration procedure is not mentioned here.

 NOTE:

Advertise the IP address of the loopback interface used as the LSR-ID through OSPF.

After the configuration, the OSPF neighbor relationship can be established between the ASBRs and the PEs in the same AS. Running the display ospf peer command, you can find that the neighbor status is Full.

Take the display on PE2 as an example.

<PE2> display ospf peer OSPF Process 1 with Router ID 4.4.4.9 Neighbors Area 0.0.0.0 interface 162.1.1.1(Pos1/0/0)'s neighbors Router ID: 3.3.3.9 Address: 162.1.1.2 State: Full Mode:Nbr is Master Priority: 1 DR: None BDR: None MTU: 0 Dead timer due in 31 sec Neighbor is up for 00:28:11 Authentication Sequence: [ 0 ]

The ASBRs and the PEs in the same AS can learn the IP address of loopback1 from each other and ping through each other.

Configure basic MPLS functions and MPLS LDP on the MPLS backbone networks of AS 100 and AS 200 to establish LDP LSPs.

Configure the IBGP peer relationship of between AS 100 and AS 200 in the the IPv4 address family view.

For detailed configurations, see the following configuration files.

Configure the VPN instance on the PEs and configure the CEs to access the VPN instances.

 NOTE:

VPN-Target attributes of the VPN instances of the PEs in different ASs must match each other.

For detailed configurations, see the following configuration files.

Enable the capability of exchanging labeled IPv4 routes.

Establish the MP-EBGP peer relationship between PE1 and PE2.

# Configure PE1.

[PE1] bgp 100

[PE1-bgp] peer 4.4.4.9 as-number 200

[PE1-bgp] peer 4.4.4.9 connect-interface LoopBack 1

[PE1-bgp] peer 4.4.4.9 ebgp-max-hop 10

[PE1-bgp] ipv4-family vpnv4

[PE1-bgp-af-vpnv4] peer 4.4.4.9 enable

[PE1-bgp-af-vpnv4] quit

[PE1-bgp] quit

# Configure PE2.

[PE2] bgp 200

[PE2-bgp] peer 1.1.1.9 as-number 100

[PE2-bgp] peer 1.1.1.9 connect-interface LoopBack 1

[PE2-bgp] peer 1.1.1.9 ebgp-max-hop 10

[PE2-bgp] ipv4-family vpnv4

[PE2-bgp-af-vpnv4] peer 1.1.1.9 enable

[PE2-bgp-af-vpnv4] quit

[PE2-bgp] quit

Configure load balancing among EBGP and IBGP routes on PE1.

# Configure PE1.

[PE1] bgp 100

[PE1-bgp] ipv4-family vpn-instance vpn3

[PE1-bgp-vpn3] load-balancing as-path-ignore

[PE1-bgp-vpn3] maximum load-balancing eibgp 2

[PE1-bgp-vpn3] quit

[PE1-bgp] quit

Verify the configuration.

After the preceding configurations, you can view that load balancing is performed among EBGP and IBGP routes on PE1.

<PE1> display ip routing-table vpn-instance vpn3

Route Flags: R - relay, D - download to fib ------------------------------------------------------------------------------ Routing Tables: vpn3 Destinations : 4 Routes : 6 Destination/Mask Proto Pre Cost Flags NextHop Interface 10.1.1.0/24 BGP 255 0 RD 5.5.5.9 Pos2/0/0 BGP 255 0 RD 4.4.4.9 Pos1/0/0 10.2.1.0/24 BGP 255 0 RD 4.4.4.9 Pos1/0/0 BGP 255 0 RD 5.5.5.9 Pos2/0/0 10.3.1.0/24 Direct 0 0 D 10.3.1.1 GigabitEthernet3/0/0 10.3.1.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0

Configuration Files

Configuration file of PE1

# sysname PE1 # ip vpn-instance vpn3 ipv4-family route-distinguisher 300:1 vpn-target 1:1 export-extcommunity vpn-target 1:1 import-extcommunity # mpls lsr-id 1.1.1.9 mpls # mpls ldp # interface Pos1/0/0 link-protocol ppp undo shutdown ip address 172.1.1.2 255.255.255.0 mpls mpls ldp # interface GigabitEthernet3/0/0 undo shutdown ip binding vpn-instance vpn3 ip address 10.3.1.1 255.255.255.0 # interface Pos2/0/0 link-protocol ppp undo shutdown ip address 192.2.1.1 255.255.255.0 mpls mpls ldp # interface LoopBack1 ip address 1.1.1.9 255.255.255.255 # bgp 100 peer 2.2.2.9 as-number 100 peer 2.2.2.9 connect-interface LoopBack1 peer 4.4.4.9 as-number 200 peer 4.4.4.9 ebgp-max-hop 10 peer 4.4.4.9 connect-interface LoopBack1 peer 5.5.5.9 as-number 100 peer 5.5.5.9 connect-interface LoopBack1 # ipv4-family unicast undo synchronization import-route direct peer 2.2.2.9 enable peer 2.2.2.9 label-route-capability peer 4.4.4.9 enable peer 5.5.5.9 enable # ipv4-family vpnv4 policy vpn-target peer 4.4.4.9 enable peer 5.5.5.9 enable # ipv4-family vpn-instance vpn3 import-route direct maximum load-balancing eibgp 2 load-balancing as-path-ignore peer 10.3.1.2 as-number 65002 # ospf 1 area 0.0.0.0 network 1.1.1.9 0.0.0.0 network 172.1.1.0 0.0.0.255 network 192.2.1.0 0.0.0.255 # return

Configuration file of ASBR1

# sysname ASBR1 # mpls lsr-id 2.2.2.9 mpls # mpls ldp # interface Pos1/0/0 link-protocol ppp undo shutdown ip address 172.1.1.1 255.255.255.0 mpls mpls ldp # interface Pos2/0/0 link-protocol ppp undo shutdown ip address 192.1.1.1 255.255.255.0 mpls # interface LoopBack1 ip address 2.2.2.9 255.255.255.255 # bgp 100 peer 1.1.1.9 as-number 100 peer 1.1.1.9 connect-interface LoopBack1 peer 192.1.1.2 as-number 200 # ipv4-family unicast undo synchronization network 1.1.1.9 255.255.255.255 network 172.1.1.0 255.255.255.0 import-route direct peer 1.1.1.9 enable peer 1.1.1.9 route-policy policy2 export peer 1.1.1.9 label-route-capability peer 192.1.1.2 enable peer 192.1.1.2 route-policy policy1 export peer 192.1.1.2 label-route-capability # ospf 1 area 0.0.0.0 network 2.2.2.9 0.0.0.0 network 172.1.1.0 0.0.0.255 # route-policy policy1 permit node 1 apply mpls-label # route-policy policy2 permit node 1 if-match mpls-label apply mpls-label # return

Configuration file of ASBR2

# sysname ASBR2 # mpls lsr-id 3.3.3.9 mpls # mpls ldp # interface Pos1/0/0 link-protocol ppp undo shutdown ip address 162.1.1.1 255.255.255.0 mpls mpls ldp # interface Pos2/0/0 link-protocol ppp undo shutdown ip address 192.1.1.2 255.255.255.0 mpls # interface LoopBack1 ip address 3.3.3.9 255.255.255.255 # bgp 200 peer 4.4.4.9 as-number 200 peer 4.4.4.9 connect-interface LoopBack1 peer 192.1.1.1 as-number 100 # ipv4-family unicast undo synchronization network 4.4.4.9 255.255.255.255 network 162.1.1.0 255.255.255.0 import-route direct peer 4.4.4.9 enable peer 4.4.4.9 route-policy policy4 export peer 4.4.4.9 label-route-capability peer 192.1.1.1 enable peer 192.1.1.1 route-policy policy3 export peer 192.1.1.1 label-route-capability # ospf 1 area 0.0.0.0 network 3.3.3.9 0.0.0.0 network 162.1.1.0 0.0.0.255 # route-policy policy3 permit node 1 apply mpls-label # route-policy policy4 permit node 1 if-match mpls-label apply mpls-label # return

Configuration file of PE2

# sysname PE2 # ip vpn-instance vpn3 ipv4-family route-distinguisher 300:1 vpn-target 1:1 export-extcommunity vpn-target 1:1 import-extcommunity # mpls lsr-id 4.4.4.9 mpls # mpls ldp # interface Pos1/0/0 link-protocol ppp undo shutdown ip address 162.1.1.2 255.255.255.0 mpls mpls ldp # interface GigabitEthernet2/0/0 undo shutdown ip binding vpn-instance vpn3 ip address 10.2.1.1 255.255.255.0 # interface LoopBack1 ip address 4.4.4.9 255.255.255.255 # bgp 200 peer 1.1.1.9 as-number 100 peer 1.1.1.9 ebgp-max-hop 10 peer 1.1.1.9 connect-interface LoopBack1 peer 3.3.3.9 as-number 200 peer 3.3.3.9 connect-interface LoopBack1 # ipv4-family unicast undo synchronization peer 1.1.1.9 enable peer 3.3.3.9 enable peer 3.3.3.9 label-route-capability # ipv4-family vpnv4 policy vpn-target peer 1.1.1.9 enable # ipv4-family vpn-instance vpn3 import-route direct peer 10.2.1.2 as-number 65001 # ospf 1 area 0.0.0.0 network 4.4.4.9 0.0.0.0 network 162.1.1.0 0.0.0.255 # return

Configuration file of PE3

# sysname PE3 # ip vpn-instance vpn3 ipv4-family route-distinguisher 300:1 vpn-target 1:1 export-extcommunity vpn-target 1:1 import-extcommunity # mpls lsr-id 5.5.5.9 mpls # mpls ldp # interface Pos2/0/0 link-protocol ppp undo shutdown ip address 192.2.1.2 255.255.255.0 mpls mpls ldp # interface GigabitEthernet1/0/0 undo shutdown ip binding vpn-instance vpn3 ip address 10.1.1.1 255.255.255.0 # interface LoopBack1 ip address 5.5.5.9 255.255.255.255 # bgp 100 peer 1.1.1.9 as-number 100 peer 1.1.1.9 connect-interface LoopBack1 peer 10.1.1.2 as-number 65001 # ipv4-family unicast undo synchronization import-route direct peer 1.1.1.9 enable # ipv4-family vpnv4 policy vpn-target peer 1.1.1.9 enable # ipv4-family vpn-instance vpn3 import-route direct peer 10.1.1.2 as-number 65001 # ospf 1 area 0.0.0.0 network 5.5.5.9 0.0.0.0 network 192.2.1.0 0.0.0.255 # return

Configuration file of CE1

# sysname CE1 # interface GigabitEthernet1/0/0 undo shutdown ip address 10.1.1.2 255.255.255.0 # interface GigabitEthernet2/0/0 undo shutdown ip address 10.2.1.2 255.255.255.0 # bgp 65001 peer 10.1.1.1 as-number 100 peer 10.2.1.1 as-number 200 # ipv4-family unicast undo synchronization import-route direct peer 10.1.1.1 enable peer 10.2.1.1 enable # return

Configuration file of CE2

# sysname CE2 # interface GigabitEthernet1/0/0 undo shutdown ip address 10.3.1.2 255.255.255.0 # bgp 65002 peer 10.3.1.1 as-number 100 # ipv4-family unicast undo synchronization peer 10.3.1.1 enable # return