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Q&A of webinar on BGP Fundamentals and Configuration [Issue 9]

Latest reply: Jan 14, 2022 05:27:43 1218 9 4 0 0

Q&A of Webinar on  BGP Fundamentals and Configuration [Issue 9]

 Questions What is BGP ORF, ADD-PATH and ROUTE REFRESH?

  • BGP ORF indicates the BGP outbound route filtering. The Outbound Route Filtering Capability defined in [BGP-ORF] provides a mechanism for a BGP speaker to send to its BGP peer a set of Outbound Route Filters (ORFs) that can be used by its peer to filter its outbound routing updates to the speaker.

 Questions What is the order of preference of attributes when some or all are applied to one neighbor in BGP?

 Questions Do We Need to Follow 3-Way Handshake Process To Establish BGP Communication?

  • Yes. BGP runs on the port TCP 179, as the TCP request, it requires three-way handshake to establish the TCP session.

 Questions Types of BGP Routing Table?

  • For different family addresses, BGP maintains different routing tables. The commonly BGP routing table includes BGP VPNv4 routing table, BGP VPNv6 routing table, BGP IPv4 routing table, BGP IPv6 routing table, BGP multicast routing table and so on.

 Questions If My BGP Neighbor Is Stuck in Idle or Active State, What Should I Do?

  • The BGP stuck in Active state or Idle state usually indicates the TCP session establishing failure between the BGP peers. You might check the network reachability of the two BGP peers, especially the TCP 179, or/and the BGP configuration.

 Questions Where to prefer EBGP over IBGP within an organisation?

  • For a user whose network doesn't scale in a wide geographical area, usually, one AS is used. Between the different geographical areas, multi ASs are used. As a special example, the BGP confederation uses the EBGP peer in the same geographical area.

 Questions Is the configuration of BGP the same between two AS with different vendors equipment (Routers)?

  • Not exactly. To establish BGP peer relationship, the basic configuration should be the same. But for the route controlling, the personalized configuration is allowed.

 Questions BGP peer relationships fail to be set up. What will be the common causes of this problem?

 Questions When EBGP peers advertise routes to each other, if a routing policy is applied in the outbound direction of the local end, the local-preference value in the apply command does not take effect why?

  • The local_preference attribute applies to the routing within an AS rather than be advertised to the outside of the AS.

 Questions When IBGP peers advertise routes to each other using a routing policy, the MED value in the apply command takes effect. When an IBGP peer advertises the learned route to an EBGP peer, then what will be the scenario?

  • MED is an optional non-transitive attribute, when receiving from the EBGP peers, it will be transmitted to its IBGP peers, but MED will not advertised to the EBGP peers.

 Questions What is relationship BGP and anycast routing and how to implementing anycast routing over BGP?

  • BGP is a route protocol, while anycast is a mechanism in which a collection of servers share the same IP address and send data from a source computer to the server that is topographically the closest. Actually, they are two totally different concepts. BGP anycast uses one or more ASs to send the same IP in different areas, based on the BGP route selection rules, the shortest AS-PATH will be selected as the best route, so that the connection is optimized.

 Questions Can we control incoming traffic form multiple ISP, without touching any router ISP/PE? Let’s say, we want to achieve same load balance any router CE for incoming traffic.

 Questions I know that BGP is an EGP, but in my research, I saw EBGP and IBGP, finally, BGP is it an EGP or an IGP? How is it possible to BGP to run like EGP and like IGP at the same time?

  • EBGP indicates the BGP peer relationship established between the different ASs, IBGP indicates the BGP peer relationship established in the same AS. It's a different concept from the EGP and IGP.

 Questions What is the finite state machine of BGP?

  • The BGP Finite State Machine (FSM) has six states: Idle, Connect, Active, OpenSent, OpenConfirm, and Established.

  • In the Idle state, BGP denies all connection requests. This is the initial status of BGP.

  • In the Connect state, BGP decides subsequent operations after a TCP connection is established. When TCP connection establishes successfully, it will migrate to OpenSent state, otherwise to the Active state.

  • In the Active state, BGP attempts to establish a TCP connection.

  • In the OpenSent state, BGP is waiting for an Open message from the peer. Once the Open message is received and no error checked, the device will send the Keepalive message to negotiate the Keepalive timer.

  • In the OpenConfirm state, BGP is waiting for a Notification or Keepalive message.

  • In the Established state, BGP peers can exchange Update, Route-refresh, Keepalive, and Notification messages.

 Questions What kind of packets does BGP uses and which are their function?

 Questions What are the loop prevention mechanism in BGP?

  • Between different ASs, BGP doesn't accept the routes which carry the same AS number, in the AS, IBGP peer doesn't spread the routes learned from the IBGP peer to other IBGP peers.

Questions How to configure BGP to handle traffic other than IPv4? Ex: IPv6

  • BGP supports the IPv6, but you should configure it in the IPv6 address family.

 Questions How to influence from my own AS the way the traffic leaves or enter my AS while using dual homed connections?

  • To influence the outgoing traffic, you can set the local-preference. To influence the entering traffic, you can set the MED value.

 Questions How is the BGP scale better than the OSPF/ISIS? Which aspect of the BGP helps it to scale better?

  • BGP is designed to deal with large size of network, it can carry much more prefixes than OSPF or ISIS does. BGP provides multi ways to control the route spreading, and unlike the link state route protocol, such as OSPF and ISIS, BGP doesn't frequently calculate the routing when the link down or flapping, which doesn't burden the routers.

 Questions What is the difference between E-BGP and MP-BGP?

  • EBGP refers to the BGP peer relationship between two different ASs, MP-BGP refers to the Multiprotocol Extensions for BGP. MP-BGP is an extension to Border Gateway Protocol (BGP) that allows different types of addresses (known as address families) to be distributed in parallel. Whereas standard BGP supports only IPv4 unicast addresses, Multiprotocol BGP supports IPv4 and IPv6 addresses and it supports unicast and multicast variants of each.

 Questions What is route reflector and why it is required?

  • Route reflector, also called RR, is designed for terminating the obstruction of route spreading in the same AS, also known as horizon split. RR could reflect the IBGP routes between the client and non-client.

 Questions Do internal BGP (iBGP) sessions modify the next hop?

  • No, IBGP sessions doesn't modify the next hop.

 Questions Do external BGP (eBGP) sessions between confederations modify the next hop?

  • No, the confederation EBGP doesn't modify the next hop either. Actually, all the IBGP rules is suitable for the confederation EBGP peers.

 Questions In external BGP (eBGP) sessions, which IP address is sent as the next hop?

  • In the EBGP peer relationship, the neighbor IP will be the EBGP routes' next hop.

 Questions What are the benefits of configuring BGP peer groups?

  •  Peer group could save the configuration workload.

 Questions What is the BGP path selection criteria?

  • BGP route selection rules, kindly refer to

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Created Jul 3, 2020 19:40:26

Good Summary
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Created Jul 3, 2020 21:59:58

Interesting knowledge
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Created Jul 3, 2020 22:00:09

thank you for sharing
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MVE Created Jul 6, 2020 09:42:53

Very important knowledge
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Created Jul 7, 2020 22:49:08

Thank u for the information
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Created Jul 13, 2020 08:31:08

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Created Aug 2, 2020 13:52:13

thanks for sharing
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Created Jan 26, 2021 11:24:41

HI, Where can i find the recording for this Webinar?
Please assist .
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Created Jan 14, 2022 05:27:43

Very Good
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