[已解决]使用ISC DHCPd做CMTS的DHCP服务器遇到个别CM无法获取IP的问题

besro

最近在研究基于LDAP管理的ISC DHCPd系统，在一个服务器中安装了OpenLDAP以及isc-dhcp-ldap-3.0.5。

LDAP配置好了，dhcpd也正确连接ldap数据启动成功，使用Arris C3作为试验设备，接了：
一个懒猫CM803
一个宏想WM102
一个Cisco/SA EPC2100
一个摩托罗拉SB5100E

结果EPC2100和SB5100E总是停留在init(d)阶段，就是说无法获得DHCP服务器分配IP：

DS/US     Prim Online    Timing Rec   CPE   IP address      MAC address    DOC  
Interface SID  state     offset power                                          
C1/0/U3.0 4    init(d)      804 12.0  0/1   0.0.0.0         0022.ceff.1ce2 D1.0
C1/0/U3.0 5    online       509 11.8  1/5   10.197.95.253   001a.92a7.7a56 D2.0A
C1/0/U3.0 6    online       507 12.0  0/5   10.197.94.254   000f.8ac1.1285 D2.0A
C1/0/U3.0 7    init(d)      816 12.0  0/1   0.0.0.0         0013.71d8.c5be D1.0

在dhcp服务器使用tcpdump 67端口，发现：
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
15:28:21.160031 IP 10.***.4.163.bootps > 10.***.255.11.bootps: BOOTP/DHCP, Request from 00:0f:8a:c1:12:85, length: 978
15:28:22.000368 IP 10.***.255.11.bootps > 10.***.88.1.bootps: BOOTP/DHCP, Reply, length: 302
15:28:22.099094 IP 10.***.4.163.bootps > 10.***.255.11.bootps: BOOTP/DHCP, Request from 00:1a:92:a7:7a:56, length: 978
15:28:23.000212 IP 10.***.255.11.bootps > 10.***.88.1.bootps: BOOTP/DHCP, Reply, length: 302
15:28:23.009433 IP 10.***.4.163.bootps > 10.***.255.11.bootps: BOOTP/DHCP, Request from 00:0f:8a:c1:12:85, length: 978
15:28:23.011788 IP 10.***.255.11.bootps > 10.***.88.1.bootps: BOOTP/DHCP, Reply, length: 302
15:28:23.024761 IP 10.***.4.163.bootps > 10.***.255.11.bootps: BOOTP/DHCP, Request from 00:1a:92:a7:7a:56, length: 978
15:28:23.026782 IP 10.***.255.11.bootps > 10.***.88.1.bootps: BOOTP/DHCP, Reply, length: 302
15:28:47.535662 IP 10.***.4.163.bootps > 10.***.255.11.bootps: BOOTP/DHCP, Request from 00:13:71:d8:c5:be, length: 442
15:28:48.000418 IP 10.***.255.11.bootps > 10.***.88.1.bootps: BOOTP/DHCP, Reply, length: 302
15:28:50.533984 IP 10.***.4.163.bootps > 10.***.255.11.bootps: BOOTP/DHCP, Request from 00:13:71:d8:c5:be, length: 442
15:28:50.535089 IP 10.***.255.11.bootps > 10.***.88.1.bootps: BOOTP/DHCP, Reply, length: 302
15:28:57.534056 IP 10.***.4.163.bootps > 10.***.255.11.bootps: BOOTP/DHCP, Request from 00:13:71:d8:c5:be, length: 442
15:28:57.535198 IP 10.***.255.11.bootps > 10.***.88.1.bootps: BOOTP/DHCP, Reply, length: 302
15:29:12.534230 IP 10.***.4.163.bootps > 10.***.255.11.bootps: BOOTP/DHCP, Request from 00:13:71:d8:c5:be, length: 442
15:29:12.535344 IP 10.***.255.11.bootps > 10.***.88.1.bootps: BOOTP/DHCP, Reply, length: 302
15:29:21.542336 IP 10.***.4.163.bootps > 10.***.255.11.bootps: BOOTP/DHCP, Request from 00:22:ce:ff:1c:e2, length: 453
15:29:22.000248 IP 10.***.255.11.bootps > 10.***.88.1.bootps: BOOTP/DHCP, Reply, length: 302
15:29:26.540791 IP 10.***.4.163.bootps > 10.***.255.11.bootps: BOOTP/DHCP, Request from 00:22:ce:ff:1c:e2, length: 453
15:29:26.541858 IP 10.***.255.11.bootps > 10.***.88.1.bootps: BOOTP/DHCP, Reply, length: 302
15:29:35.540904 IP 10.***.4.163.bootps > 10.***.255.11.bootps: BOOTP/DHCP, Request from 00:22:ce:ff:1c:e2, length: 453
15:29:35.541989 IP 10.***.255.11.bootps > 10.***.88.1.bootps: BOOTP/DHCP, Reply, length: 302

上述红色的能获得IP，蓝色的就不能了……

10.***.255.11   dhcp服务器
10.***.4.163     CMTS IP
10.***.88.1       CMTS中CM的路由IP

以前测试过使用不带LDAP的ISC DHCPd，发现只有3.0.1及以下的版本才没有这类问题，经过进一步分析3.0.1与3.0.5版本之间在响应dhcp请求时的数据差别，发现：

3.0.1
________________________________
17:01:34.000416 IP (tos 0x0, ttl  64, id 0, offset 0, flags [DF], proto 17, length: 330) 10.***.255.11.bootps > 10.***.88.1.bootps: BOOTP/DHCP, Reply, length: 302, hops:1, xid:0x308c400, flags: [Broadcast]
          Your IP: 10.197.95.253
          Server IP: 10.***.255.11     ←更高的版本没有这项了
          Gateway IP: 10.***.88.1
          Client Ethernet Address: 00:1a:92:a7:7a:56 [|bootp]

3.0.5
________________________________
17:36:01.000229 IP (tos 0x0, ttl  64, id 0, offset 0, flags [DF], proto 17, length: 330) 10.***.255.11.bootps > 10.***.88.1.bootps: BOOTP/DHCP, Reply, length: 302, hops:1, xid:0x36403d40, flags: [Broadcast]
          Your IP: 10.197.95.253
          Gateway IP: 10.***.88.1
          Client Ethernet Address: 00:1a:92:a7:7a:56 [|bootp]

初步怀疑就是没有ReplyServer IP: 10.***.255.11导致，盼望高手分析。

－－－－－－－－－－－－－－－－－－－－

原因在于3.0.1版本后，必须指定启动文件服务器next-server参数……之前的版本不需要设置，默认是本机……哎……误导了

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