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Trunk Load Balancing Fails on an ME60 at the User Side.

Publication Date:  2013-01-07 Views:  20 Downloads:  0
Issue Description

1.         Version: ME60 V600R002C02SPC700

2.         Problem description: An ME60 at a site is attached to an S9300 to provide bandwidth access services for users. The interfaces on the ME60 and the S9300 are bundled together to form a trunk interface. The bandwidth usage of one link is nearly 100%, but the bandwidth usage of the other link is only 2%.

    Interface                      PHY   Protocol InUti OutUti   inErrors  outErrors

    Aux0/0/1                    *down   down        0%     0%          0          0

    Eth-Trunk0                    up     down       50%    49%        0          0

    GigabitEthernet2/0/7    up      up          98%    97%         0          0

    GigabitEthernet2/0/8    up      up           2%     1%         0          0

Handling Process

1.         The on-site Huawei technical support personnel check the ME60 configuration. They do not find configurations of static routes, routing policy or ACL that cause load unbalancing.

2.         Since the services are affected, they run the shutdown command and then the undo shutdown command on GE 2/0/7 to rehash the result for trunk load balancing. However, the problem persists after the preceding configurations are complete.

3.         Trunk load balancing on the user side uses the hash algorithm based on CAR. The interface configurations are as follows.

 < XXX-HW-ME60-B1>dis static-user interface Eth-Trunk 0.4

   ---------------------------------------------------------------------------

   Interface       VLAN-ID        IP-address      MAC-address      VPN

   ---------------------------------------------------------------------------

   Eth-Trunk0.4    4000           121.31.56.25             -                --       

   Eth-Trunk0.4    4000           121.31.56.26            -                --       

   Eth-Trunk0.4    4000           121.31.56.27            -                --       

   Eth-Trunk0.4    4000           121.31.56.28             -                --    

   ---------------------------------------------------------------------------

   Total 1034 item(s) matched 

  

<XXX-HW-ME60-B1>dis access-user interface Eth-Trunk 0.3

  ------------------------------------------------------------------------------

  UserID  Username                Interface      IP address       MAC

          IPv6 address

  ------------------------------------------------------------------------------

  1534    XXX-HW-ME60-B1-0...  Eth-Trunk0.3  221.7.251.204   0004-6794-fbf4

          -

  7753    XXX-HW-ME60-B1-0...  Eth-Trunk0.3   221.7.251.171  0004-6794-fb59

          -

  10932   XXX-HW-ME60-B1-0...  Eth-Trunk0.3   221.7.251.151     0025-9e1a-f6ef

         -

  53740   XXX-HW-ME60-B1-0...  Eth-Trunk0.3   221.7.250.91     0004-6797-aa03

          -

  55243   XXX-HW-ME60-B1-0...  Eth-Trunk0.3   221.7.251.60    0004-6791-e7aa

          -

  57236   XXX-HW-ME60-B1-0...  Eth-Trunk0.3   221.7.251.101     0004-6794-f776

                                             

  ------------------------------------------------------------------------------

  Normal users                   : 673

  RUI Local users               : 0

  RUI Remote users          : 0

  Total users                        : 673        

4.         The access rate of static users in the domain to which Eth-Trunk0.4 is bound is not limited. The access rate of dial-up users in the domain to which Eth-Trunk0.3 is bound is limited using the RADIUS server.

Root Cause

The possible causes are as follows:

The static routes are configured, causing some traffic to be forwarded through a specified interface.

A routing policy is configured in each domain, causing the user traffic in a specific domain to be forwarded through a single interface.

ACL is configured, so some traffic is forwarded through a specified interface, causing load imbalance.

Trunk load balancing on an ME60 running V600R002C02 at the user side is implemented using a hash algorithm based on the user-defined CAR and the user number. This hash algorithm may cause the load imbalance.

Solution

Limit the access rate of the static users in the domain. Then run the shutdown and undo shutdown commands to rehash the result.

Suggestions
1. The hash algorithm for Trunk load balancing based on the CIR on ME60s running V600R002C02 is as follows. If the CIR is configured, the users that go online through the trunk interface will compare all the CIR values configured on the member interfaces that are Up and finds the AFQ with the smallest CIR value. The users go online through the member interface with this AFQ. The user traffic whose rate is not limited is hashed with the CIR value 128 kbit/s. If all user traffic is forwarded through the same trunk interface regardless of whether the access rate is limited or not. 2. A member interface is selected based on the following rules: Hash the configured CIR value if the access rate is limited. Hash the CIR 128 kbit/s if the access rate is not limited. However, the actual user traffic is not determined if the access rate is not limited, which may be far larger than 128 kbit/s. As a result, load imbalance may occur. Therefore, limit the access rate of the static users as needed during network planning. If users with high bandwidths or without access rate limit want to go online, separating these users from common users is recommended so that the user traffic is forwarded through different trunk interfaces. 3. The hash algorithm for load balancing based on the user number on ME60s running V600R002C02 is as follows. The users compare all member interfaces that are Up and find the member interface with the smallest user number. The users go online through this member interface by configuring the bas-load-balance command on the Eth-Trunk interface view.

END