DHCP sending incorrect gateway in DHCP Reply
Eric Koons
ekoons5159 at gmail.com
Wed Oct 16 14:07:11 UTC 2019
I’m having an issue with ISC DHCP where it’s sending the incorrect router option/gateway in the DHCP reply. Any help is appreciated.
Below is a capture using TCPDUMP on the DHCP server. With this particular request, it should be sending the Gateway of 10.123.4.41, but it’s sending 10.123.4.49 which is the gateway option defined in the other scope. It almost seems like the first device in a DHCP scope that comes online the Server uses that as the router option for all other requests. I’ve also attached a copy of the dhcpd.conf file below. This is on a CENTOS server: CentOS Linux release 7.7.1908 (Core).
09:57:27.101056 00:a5:bf:9d:a9:59 > 00:50:56:ae:be:10, ethertype IPv4 (0x0800), length 442: (tos 0xc0, ttl 29, id 53170, offset 0, flags [none], proto UDP (17), length 428)
10.123.4.41.bootps > 10.123.0.9.bootps: [udp sum ok] BOOTP/DHCP, Request from 00:18:48:02:6e:a0, length 400, xid 0xcc58406, Flags [none] (0x0000)
Gateway-IP 10.123.4.41
Client-Ethernet-Address 00:18:48:02:6e:a0
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Request
Server-ID Option 54, length 4: 10.123.0.9
Requested-IP Option 50, length 4: 10.123.4.45
Parameter-Request Option 55, length 12:
Subnet-Mask, BR, Time-Zone, Default-Gateway
Domain-Name, Domain-Name-Server, Hostname, Vendor-Option
Time-Server, BF, TFTP, WWW
Vendor-Option Option 43, length 86: 2.3.82.80.68.3.9.69.67.77.58.101.83.65.70.69.4.7.57.49.48.52.50.48.53.5.5.48.46.48.46.49.6.7.49.95.53.48.95.50.51.7.5.48.46.48.46.49.8.6.48.48.49.56.52.56.9.6.53.50.48.48.48.49.10.20.86.101.99.105.109.97.32.78.101.116.119.111.114.107.115.32.73.110.99.46
Vendor-Class Option 60, length 3: "RPD"
Client-ID Option 61, length 15: hardware-type 255, 48:02:6e:a0:00:03:00:01:00:18:48:02:6e:a0
Agent-Information Option 82, length 18:
Circuit-ID SubOption 1, length 6: ^@^D^@^@^@^C
Remote-ID SubOption 2, length 8: ^@^F^@M-^^^^]YM-^
END Option 255, length 0
09:57:27.101623 00:50:56:ae:be:10 > 00:00:0c:07:ac:00, ethertype IPv4 (0x0800), length 381: (tos 0x0, ttl 64, id 62282, offset 0, flags [DF], proto UDP (17), length 367)
10.123.0.9.bootps > 10.123.4.41.bootps: [bad udp cksum 0x1a94 -> 0xcaaa!] BOOTP/DHCP, Reply, length 339, xid 0xcc58406, Flags [none] (0x0000)
Your-IP 10.123.4.45
Gateway-IP 10.123.4.41
Client-Ethernet-Address 00:18:48:02:6e:a0
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: ACK
Server-ID Option 54, length 4: 10.123.0.9
Lease-Time Option 51, length 4: 86400
Subnet-Mask Option 1, length 4: 255.255.255.248
BR Option 28, length 4: 10.123.4.55
Time-Zone Option 2, length 4: -18000
Default-Gateway Option 3, length 4: 10.123.4.49
Domain-Name Option 15, length 13: "rpd.sectv.com"
Domain-Name-Server Option 6, length 4: 10.123.0.9
Vendor-Option Option 43, length 10: 61.8.10.123.4.10.10.123.4.58
Time-Server Option 4, length 4: 10.123.0.9
Agent-Information Option 82, length 18:
Circuit-ID SubOption 1, length 6: ^@^D^@^@^@^C
Remote-ID SubOption 2, length 8: ^@^F^@M-^^^^]YM-^
END Option 255, length 0
Here is a copy of my dhcpd.conf:
#Global Options:
#Set the server to authoritative;
authoritative;
option domain-name-servers 10.123.0.9;
option log-servers 10.123.0.9;
option ntp-servers 10.123.0.9;
option time-servers 10.123.0.9;
local-address 10.123.0.9;
#Time Offset
option time-offset -18000;
#Lease time
default-lease-time 86400;
max-lease-time 172800;
#Time zone
option PCode code 100 = text;
option TCode code 101 = text;
option PCode "”EST5EDT4,M3.2.0/02:00,M11.1.0/02:00";
option TCode "America/New_York”";
#Remote Phy Stuff
# option CCAPCore code 43 = string;
# option iNode-manager code 43 = string;
option space VCM;
option VCM.ccap_cores code 61 = { array of ip-address };
default-lease-time 86400;
max-lease-time 172800;
# Use this to enble / disable dynamic dns updates globally.
# ddns-updates on;
# ddns-update-style interim;
# ddns-rev-domainname "in-addr.arpa";
# deny declines;
# deny bootp;
#allow client-updates;
# key dhcpupdate {
# algorithm hmac-md5;
# secret iY+hMAmhBJvhxc82gX8Vgg==;
# }
# zone sectv.com. {
# primary 10.0.40.5;
# key dhcpupdate;
# }
# zone 10.123.in-addr.arpa. {
# primary 10.0.40.5;
# key dhcpupdate;
# }
# Use this to send dhcp log messages to a different log file (you also
# have to hack syslog.conf to complete the redirection).
log-facility local7;
#10.123.0.0/24 Subnet - Management
subnet 10.123.0.0 netmask 255.255.255.0 {
#No options or ranges defined - No DHCP
}
# 10.123.4.40/29 Subnet
subnet 10.123.4.40 netmask 255.255.255.248 {
range 10.123.4.42 10.123.4.46;
option subnet-mask 255.255.255.248;
option domain-search "sectv.com";
option routers 10.123.4.41;
option broadcast-address 10.123.4.47;
# class "CiscoRPD" {
# match if option vendor-class-identifier="RPD";
vendor-option-space VCM;
option VCM.ccap_cores 10.123.4.10, 10.123.4.58;
option domain-name "rpd.sectv.com";
# }
# class "CiscoiNode"{
# match if option vendor-class-identifier="Cisco.iNode.oib.1.0";
# option iNode-manager 01:04:0a:7b:00:0a;
# option tftp-server-name "10.123.0.9";
# option bootfile-name "inode.bin";
# option domain-name "inode.sectv.com";
# }
}
# 10.123.4.48/29 Subnet
subnet 10.123.4.48 netmask 255.255.255.248 {
range 10.123.4.50 10.123.4.54;
option subnet-mask 255.255.255.248;
option domain-search "sectv.com";
option routers 10.123.4.49;
option broadcast-address 10.123.4.55;
class "CiscoRPD" {
match if option vendor-class-identifier="RPD";
vendor-option-space VCM;
option VCM.ccap_cores 10.123.4.10, 10.123.4.58;
option domain-name "rpd.sectv.com";
}
# class "CiscoiNode"{
# match if option vendor-class-identifier="Cisco.iNode.oib.1.0";
# option iNode-manager 01:04:0a:7b:00:0a;
# option tftp-server-name "10.123.0.9";
# option bootfile-name "inode.bin";
# option domain-name "inode.sectv.com";
# }
}
# 10.123.4.56/29 Subnet
subnet 10.123.4.56 netmask 255.255.255.248 {
range 10.123.4.58 10.123.4.62;
option subnet-mask 255.255.255.248;
option domain-search "sectv.com";
option routers 10.123.4.57;
option broadcast-address 10.123.4.63;
}
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.isc.org/pipermail/dhcp-users/attachments/20191016/8768f7c4/attachment.htm>
More information about the dhcp-users
mailing list