Shulou(Shulou.com)06/01 Report--

BGP Functions:

A large number of routes are transmitted in a stable manner over time between different large networks

And it allows flexible routing control while ensuring loop-free.

BGP work process:

1. Establish neighbor list;

2. Synchronous database;

3. Calculate the routing table

BGP routing principles:

1.preference-value, Huawei private attribute, only works locally on the device. The larger the value, the better;

It will not be transmitted to other routers along with the update message;

2.local-preference, local priority, the larger the better; default is 100;

3. Compare whether the route is "locally originated": locally generated is better than learned from other neighbors;

#self-generated: manual aggregation> automatic aggregation> network > import-route

#Learning from neighbors;

4.as-path , comparing the length of as-path, the shorter the better;

5. Compare origin attributes: i > e > ?

6. Compare MED, the smaller the better;

7. Compare route types, EBGP > IBGP

8. Compare the size of the Metric for the next hop to the BGP route, the smaller the better.

9. Compare the length of cluster-list, the shorter the better;

10. The comparison is originator-id, the smaller the better;

11. Compare router-id, the smaller the better;

12. Compare IP addresses of neighbor devices, the smaller the better;

BGP route announcement and delivery:

- Means of announcement:

network

--> Put the route into the BGP database;

- Transmission:

1. When routing between external BGP neighbors, the next hop is changed;

2. When routing between internal BGP neighbors, the next hop is invariant;

- If it does not change, it may cause the next hop to be unreachable.

Configuration command: [R1]bgp200[R1-bgp]router-id 1.1.1.1

[R1-bgp]peer 192.168.2.2 as-number 64512

Note: 192.168.2.2 must be the real IP address of the interface of the other device, and it can be communicated;

It cannot be the router-id of the other party; # as-number refers to the as number of the other party, not your own.

[R1-bgp]network 192.168.1.0 255.255.255.0

[Announcing Network Segment]

[R1-bgp]peer 192.168.2.2 next-hop-local

R1 sends routes to BGP neighbor 192.168.2.2, and the next-hop IP addresses are all

Set the IP address used when establishing neighbors with each other;

Note:

Routes in BGP databases, when optimized, have the following two behaviors:

1. putting the route into a local routing table;

2. Send the route to BGP neighbors

BGP Anti-Looping Mechanism in AS: IEGP Horizontal Split

A BGP router receives a route in a host's IBGP neighbor and does not reroute it to another of its IBGP neighbors.

IBGP horizontal segmentation solution:

1 -IBGP Neighborhood Full Interconnection

2 - BGP Alliance

3 - BGP route reflector

Attribute changes for BGP routes:

1. Grab routes of interest

2. Configure routing policies, change attributes for routes of interest

3. calls the policy

route-policy distinguished by different names

route-policy consists of multiple entries, each distinguished by a different node /sequence number;

route-policy During execution, policy matching is performed starting from the smallest node number to the largest node number

If a node entry matches, stop matching. You won't see the following entry;

If there is an explicit match, the match continues until the last "Implicit Deny All"

route-policy ends with an implicit rejection of all entries:

route-policy {name} deny node {maximum number}

It does not contain any "if-match" statements, meaning match all.

How route-policy indicates that all are allowed:

route-policy {name} permit node {maximum number}

There is no need to write any match statements;

[R3]ip ip-prefix 123 permit 20.20.20.0 24

[Allow ip prefix to match 20.20.20.0 segment]

[R3]route-policy 456 permit node 10

AAA routing policy sequence is 10

[R3-route-policy]if-match ip-prefix 123

Matching Strategy 123

[R3-route-policy]apply local-preference 200

[This policy will be applied if the match is successful. Priority is 200]

[R3-bgp]peer 192.168.2.1 route-policy 456 export

[Enable policy for neighbors to be applied on egress port]

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.