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Tag Archives: Huawei router

IP prefix list to filter routes

How to filter advertised and received routes on Huawei router?

Let’s try to check it based on the following topology:

  1. Configure basic OSPF functions on all routers.
  2. Configure static routes on AR1 router and import them to OSPF.
  3. Use filter-policy for advertised routes on AR1.
  4. Use filter-policy for received routes on AR3.

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how to find “TTL exceeded” packets

Let’s imagine you are an IP engineer and suddenly found increasing number of “TTL exceeded” packets on your router. Your first thought is “what the hell is it? How to find a source of these packets?”

Take it easy. You will know how to investigate such issue on Huawei router.

[labnario]display ip statistics
  Input:     sum               2783201      local               2321967
             bad protocol            0      bad format                0
             bad checksum            0      bad options               0
             discard srr             0      TTL exceeded         494196
  Output:    forwarding              0      local                886008
             dropped                 0      no route                  0
  Fragment:  input                   0      output                    0
             dropped                 0
             fragmented              0      couldn't fragment         0
  Reassembling:sum                   0      timeouts                  0

As you can see there are “TTL exceeded” packets. “Display ip statistics” command shows packets that are directed to CPU. Don’t mix it up with packets found on the interface. For example, you don’t have dropped packets on the interface but “display ip statistics” shows such packets.

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BGP LocPref once again

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.

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BGP default local preference in Huawei CLI

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.

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MPLS L3VPN on Huawei routers

  1. CE1 and CE5 are in VPN labnario_1
  2. CE2 and CE8 are in VPN labnario_2
  3. ISIS level -2 as IGP
  4. Connections CE1—PE3 and CE5—PE4 – static routes
  5. Connection CE2—PE3 – OSPF
  6. Connection CE8—PE4 – EBGP
  7. Users in different VPNs cannot access each other.

A BGP/MPLS IP VPN uses the Border Gateway Protocol (BGP) to advertise VPN routes and the Multiprotocol Label Switching (MPLS) to forward VPN packets on backbone networks.

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