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DHCP Access Users Fail to Obtain Correct Masks Due to the Incorrect Attribute Delivered by RADIUS

Publication Date:  2013-09-27 Views:  29 Downloads:  0
Issue Description
Access users went online in DHCP mode. The RADIUS allocated IP addresses to users, and the users could go online. However, the IP addresses obtained by the users had 32-bit masks, but the mask configured on the RADIUS was 24 bits long.
Handling Process

Possible causes were as follows:

1. The RADIUS or BAS was configured incorrectly.

2. The BAS software had a bug.

Based on the preceding possible causes, Huawei performed the following operations to diagnose the fault:

1. Debugged DHCP and found that DHCP Ack packets carried 32-bit masks.

*0.3883652931 bng0 DHCR/7/debug2: 

  [ DHCPR send to client ] : =====

  [ Xid   ]:1795360822 

  [ cmd   ]:2  

  [ Htype ]:1   

  [ Hlen  ]:6   

  [ Hops  ]:0   

  [ Secs  ]:0   

  [ Flag  ]:0   

  [ Ciadd ]:0.0.0.0

  [ Yiadd ]:94.72.14.2

  [ Siadd ]:0.0.0.0

  [ Giadd ]:94.72.14.1 chaddr:0022-6b7a-0220

  [ Sname ]: 

  [ File  ]: 

  [ Option ]:-----

  Message type:ACK

  Route ip:94.72.14.1

  Subnet mask:255.255.255.255

  Server id:94.72.1.182

  Dns:62.152.64.133 255.255.255.255

  leasetime:180s

  Renewtime:90s

  Rebindtime:135s

  Option82 :RID:,CID: 

Debugged the RADIUS and found that it delivered 24-bit masks.

  [Framed-IP-Address(8)               ] [6 ] [94.72.14.2]

  [Session-Timeout(27)                ] [6 ] [86400]

  [Framed-IP-Netmask(9)               ] [6 ] [255.255.255.0]

  [HW-Gateway-Address(HUAWEI-73)      ] [6 ] [94.72.14.1]

2. The Framed-IP-Netmask attribute should be delivered to PPP users. For DHCP access users, the Huawei proprietary attribute HW-Subnet-Mask(HUAWEI-72) should be delivered.

3. Changed the attribute delivered by the RADIUS, and the issue was resolved.
Root Cause

The attribute delivered by the RADIUS was incorrect.

The Framed-IP-Netmask attribute should be delivered to PPP users. For DHCP access users, the Huawei proprietary attribute HW-Subnet-Mask(HUAWEI-72) should be delivered.
Solution
The Framed-IP-Netmask attribute was changed to the HW-Subnet-Mask(HUAWEI-72) attribute.
Suggestions
None

END