Tag Archives: Huawei CLI

Let’s keep going and try to configure BGP local preference attribute using route-policy.

We can take full advantage of topology and configuration from the last post: “BGP default local preference in Huawei CLI“.

1. Assure full connectivity based on the attached topology (look at the previous article).
2. Configure Loopback 10 and Loopback 20 on router AR4.
3. Import all Loopback interfaces of router AR4 to BGP.

Let’s assume that we have a topology like in below picture:

1. AR1, AR2 and AR3 are in AS 100.
2. AR4 is in AS 200.
3. Loopback 100 of router AR1 and loopback 0 of router AR4 are advertised by BGP.

What we want to do is to configure default local preference attribute, which will determine the optimal route, for traffic that leaves AS 100. In our case, the whole traffic leaving AS 100 will go through AR3.

If a BGP device obtains multiple routes from different IBGP peers and these routes have different next hops to the same destination, the BGP device will select the route with the greatest Local_Pref value.

Today a few words about 2 simple but useful commands: lock and send.

LOCK – prevents unauthorized users from operating on the current terminal interface

SEND – enables the system to transfer messages between user interfaces

Let’s look how they work on Huawei S5700 switch.

LOCK

<labnario>lock
Enter Password:
Confirm Password:

 Info: The terminal is locked. 

Enter Password:

<labnario>

Topology Change (TC) packets are sent when MSTP-enabled interface in a network flaps. If a physical interface frequently alternates between Up and Down, the MSTP status of the device in the network becomes unsteady. As a result, a large number of TC messages are generated, ARP entries are frequently deleted and services are interrupted.

How to find the source of TC packets?

Let’s look at the log, generated on one of the switches in a network. Let’s take Huawei S9300 switch as an example:

Dec 19 2012 11:32:56+10:00 S9300 %%01MSTP/6/RECEIVE_MSTITC(l)[40922]:MSTP received BPDU with TC, MSTP process 0 instance 0, port name is GigabitEthernet6/0/0.

What can we find in this log?

The most important for us is the port number on which the switch received TC packet, in this case interface GE6/0/0. To troubleshoot this problem we have to go to the next switch, connected to interface GE6/0/0 and check logs of that switch. If the neighbouring switch receives TC packets as well, we have to do further troubleshooting. If we find in the logs that MSTP-enabled interface is flapping, we can consider that this interface is the source of the TC packet. If this interface is still flapping, just make it down, to avoid unsteady behaviour.

This article is a continuation of the basic BGP with Huawei CLI.

Today I want to explain you, why labnarioR5 router cannot ping BGP prefixes advertised by BGP AS50. Do you remember our BGP topology? I have configured BGP protocol as in the picture below:

There are three BGP Autonomous Systems: AS50, AS100 and AS55. All are connected via EBGP peering sessions. AS100 has three routers forming IBGP full mesh. LabnarioR1 router in AS50 advertises three prefixes:

• 11.10.10.0/24
• 12.10.10.0/24
• 13.10.10.0/24

All these prefixes are advertised by the routers in AS100 and pass to AS55. LabnarioR5 router has these prefixes in its BGP and routing tables, but cannot ping them. Why is it like that?