No relevant resource is found in the selected language.

This site uses cookies. By continuing to browse the site you are agreeing to our use of cookies. Read our privacy policy>

Reminder

To have a better experience, please upgrade your IE browser.

upgrade

The ME60 Attached Service Is Abnormal in Hot Backup Scenario Because the External DHCP Server Does Not Disabled giaddr

Publication Date:  2013-10-06 Views:  29 Downloads:  0
Issue Description
1. Symptom: The AP attached to different S8500 goes offline.
2. Networking: Two ME60s are used for the hot backup and the AP is the DHCP client. The ME60 is the DHCP-Relay and the AC is the DHCP server. To address the attainability problem, IP address 2 (IP2) and IP address 3 (IP3) are used on the two BRAS as the gateway IP addresses (giaddr). IP address 1 (IP1) is the gateway IP address of this network segment. 
 
CID:/icase/servlet/download?dlType=HtmlAreaImage&imageId=20452
Handling Process

After the DHCP RELAY receives the DHCP client broadcast packet from the service port, if the “gateway ip addr” field is 0, the primary IP address of the Layer 3 interface of the service port is filled in this field, and the packet is sent to the DHCP server in unicast mode. Because the two ME60 has the same IP address, the gateway address cannot be filled in this field. A new gateway ip addr must be specified , and the address cannot be used for the client.

1. The faulty APs are on different S8500, indicating that the fault is not caused by the S8500.
2. Log in to the BRAS to view the device configuration. No problem is found.
3. On the DHCP serve r(AC), perform ping test to giaddrs (IP2 and IP3) of the two ME60. IP2 is pinged through but IP3 is not.
4. Check the route of IP3 on the BRAS. No UNR roue is found. (In normal conditions, after the giaddr is configured, a 32-bit UNR host route is generated). A 32-bit UNR host route is generated after the giaddr is reconfigured, as shown in the following:
display ip rout vpn-instance WLAN_SR_AC1 X.239.16.3 IP3
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Table : WLAN_SR_AC1
Summary Count : 1
Destination/Mask    Proto  Pre  Cost       Flags NextHop         Interface

   X.239.16.0/21  Unr    61   0            D   127.0.0.1       NULL0    //no 32-bit host route for IP3
[ME60-dhcp-server-group-hn-wlan-ac1-10]dis this
#
dhcp-server group hn-wlan-ac1-10
 dhcp-server X.141.177.97
 dhcp-server X.141.177.98
 dhcp-server giaddr ip-address X.239.16.3 vpn-instance WLAN_SR_AC1  //the host route is generated after the route data is reconfigured
[ME60-dhcp-server-group-hn-wlan-ac1-10]display ip rout vpn-instance WLAN_SR_AC1 X.239.16.3
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Table : WLAN_SR_AC1
Summary Count : 1
Destination/Mask    Proto  Pre  Cost       Flags NextHop         Interface

    X.239.16.3/32  Unr    63   0            D   127.0.0.1       InLoopBack0

5. On the BRAS, check the IP3 offline information. It is found that the DHCP server allocates IP3 to users. The information is listed as follows:

display  aaa offline-record ip-address  IP3
  --------------------------------------------
  User name          : ME60@wlan-nms
  Domain name        : wlan-nms
  User MAC           : XXXX-XXXX-XXXX
  User access type   : IPoE
  User access interface: Eth-Trunk8.1333
  User access PeVlan/CeVlan    : 1432/0
  User IP address    : IP3
  User IPv6 address  : -
  User ID            : 97985
  User authen state  : Authened
  User acct state    : AcctReady
  User author state  : AuthorIdle
  User login time    : 2013-01-02 13:42:18
  User offline time  : 2013-01-02 13:52:56
  User offline reason: RUI request offline
  --------------------------------------------
  Are you sure to display some information?(y/n)[y]:y
  --------------------------------------------
  User name          : ME60@wlan-nms
  Domain name        : wlan-nms
  User MAC           : XXXX-XXXX-XXXX
  User access type   : IPoE
  User access interface: Eth-Trunk8.1333
  User access PeVlan/CeVlan    : 1432/0  
  User IP address    : IP3
  User IPv6 address  : -
  User ID            : 198315
  User authen state  : Authened
  User acct state    : AcctReady
  User author state  : AuthorIdle
  User login time    : 2013-01-02 12:59:33
  User offline time  : 2013-01-02 13:10:12
  User offline reason: RUI request offline
  --------------------------------------------
Root Cause
The dhcp-server giaddr ip-address is manually assigned on the active and standby devices but the addresses are not excluded. As a result, the device allocates the addresses to other users.
Solution
Exclude the giaddr.
Suggestions
To address this kind of problem, you must know well about the networking and related protocols.

END