AS28573 peering information and eBGP neighbors

interconnection points

Extensive peering arrangements are a critical component to providing outstanding connectivity and performance for the customers as well as increased service resilience through diversified routing.

Peering is the bedrock of every network and all service providers actively expand their peering capacity in line with traffic growth to maintain world class performance.

AS28573 Configuration for iBGP and eBGP

BGP is an exterior gateway protocol (EGP), used to perform interdomain routing in TCP/IP networks. A BGP router needs to establish a connection (on TCP port 179) to each of it's BGP peers before BGP updates can be exchanged. The BGP session between two BGP peers is said to be an external BGP (eBGP) session if the BGP peers are in different autonomous systems (AS). A BGP session between two BGP peers is said to be an internal BGP (iBGP) session if the BGP peers are in the same AS28573 autonomous system.

By default, the peer relationship is established using the IP address of the interface closest to the peer router. However, using the neighbor update-source command, any operational interface, including the loopback interface, can be specified to be used for establishing TCP connections. This method of peering using a loopback interface is useful since it will not bring down the BGP session when there are multiple paths between the BGP peers, which would otherwise result in tearing down the BGP session if the physical interface used for establishing the session goes down. In addition to that, it also allows the routers running BGP with multiple links between them to load balance over the available paths.

AS28573 Network Diagram

The AS28573 backbone cost burden associated with settlement-free peering traffic exchange should be equitably shared. Regardless of the direction or type of traffic exchanged between the networks, the routing practices and location or interconnection points should be such that each party bears a reasonably equal share of backbone costs.

In the case that the peering party has significant excess inbound traffic volume to deliver to AS28573 (significantly in excess of that being sent outbound by AS28573 to that party) then the parties should agree the routing behaviour expected of one another within reasonable technical, and operationally-feasible bounds.

When the peering partner has network presence in multiple countries or continents where AS28573 also has Points Of Presence, it will be desirable to open peering legs in at least two locations, and maybe more, subject to the cost/benefits of PoP build-out. This is to ensure that the traffic is exchanged optimally in the respective countries/continents and peering interconnections benefit both partners equally.

Peers must be directly connected when using eBGP. If they are not directly connected, the neighbor ebgp-multihop command must be used and a path through an IGP or static route to reach the peer must exist in order for the routers to establish neighbor relationship.

Verify iBGP/eBGP AS28573 Configuration

Use the show ip bgp neighbors command to display information about the TCP and Border Gateway Protocol (BGP) connections and verify if the BGP peer is established. The output of the show ip bgp neighbors command below shows the BGP state as 'Established', which indicates that the BGP peer relationship has been established successfully.

R1-AGS# show ip bgp neighbors | include BGP
BGP neighbor is,  remote AS 28573, internal link
  BGP version 4, remote router ID
  BGP state = Established, up for 00:04:20
  BGP table version 1, neighbor version 1

The show ip bgp neighbors command has been used above with the modifier | include BGP. This makes the output more readable by filtering the the command output and displaying the relevant parts only.

In addition, the show ip bgp summary command can also be used to display the status of all BGP connections, as shown below.

R1-AGS(9)# show ip bgp summary
BGP router identifier, local AS number 28573	
BGP table version is 1, main routing table version 1

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd      4 28573       3       3        1    0    0 00:00:26        0

AS28573 eBGP Configuration with a Loopback Address

You can also configure eBGP/iBGP using a loopback address (or any other operational interface). Loopback interfaces are used in this manner to guarantee reachability in networks with multiple paths as shown in Sample Configurations of the Load Sharing Using the Loopback Address as a BGP Neighbor section of Load Sharing with BGP in Single and Multihomed Environments.

Load balancing with Multihomed AS28573 to Two ISPs Through a Single Local Router

This case shows how to achieve load sharing when multiple links exist between a remote AS and AS28573. These links are terminated in one router at the AS28573 and on multiple routers at remote ASs in a single-homed BGP environment.

ASN IPv4 IPv6 Power
AS10429           105       0       2  
AS16735           3336       368       8  
AS1916           2681       791       4  
AS22356           596       0       7  
AS267613           1521       198       3  
AS37468           860       31       4  
AS4230           306013       220563       642  
AS52320           1034       99       4  
AS6057           0       31       1  
AS6939           4079       3176       103  
AS4230           0       3       3  
AS14840           215       31       1  
AS23106           345       40       1  
AS262317           215       31       1  
AS262757           215       31       1  
AS263075           215       31       1  
AS263508           215       0       1  
AS263584           215       0       1  
AS264911           215       31       1  
AS28186           1674       228       2  
AS28220           426       0       1  
AS28260           488       0       1  
AS28571           0       31       1  
AS28634           430       0       1  
AS42473           215       31       1  
AS52720           389       134       2  
AS52863           215       31       1  
AS52873           422       110       1  
AS53070           215       31       1  
AS57695           215       31       1  
AS61595           215       31       1