network troubleshooting quick reference

dhcp, linux, networking, pxe, quick reference

verbose tcpdump

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tcpdump -nnvvXSs 1514 -i any

tcpdump specific mac dhcp (if mac = AA:EE:DD:0c:cf:08)

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tcpdump -nnvvXSs 1514 -i any '((port 67 or port 68) and (udp[38:4] = 0x3e0ccf08))'

nc connect to udp

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nc -u host port

nc test for connction

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nc -z $address $port

test tftp

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tftp $ip
tftp> get /pxelinux.0
Transfer timed out.

tftp> get /pxelinux.0
tftp>

rhel/fedora/centos firewall command

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firewall-cmd --permanent --zone=public --add-rich-rule="rule family="ipv4" source address="10.0.0.3/32" port protocol="tcp" port="5432" accept"
success
[root@replica ~]# iptables -L -n | grep 10.0.0.3
[root@replica ~]# firewall-cmd --reload
success
[root@replica ~]# iptables -L -n | grep 10.0.0.3
ACCEPT     tcp  --  10.8.10.24           0.0.0.0/0            tcp dpt:5432 ctstate NEW