Category: Networking

Customizing Wireshark Settings

I’ve done countless troubleshooting sessions so that I’m having Wireshark open with a relevant capture file and either I’m showing my findings to the other participants or doing straight up live packet analysis. Sometimes the sessions are followed up with questions about how did I actually have Wireshark configured because it looked different on their […]

Cisco Nexus 9000 Routing Limitations

This is a memo and reminder about the routing limitations that I stumbled into when working with Nexus 9000 series switches running NX-OS. Feature Limitation Link to documentation PBR You cannot configure PBR on port-channel subinterfaces Interfaces configuration guide for 9.3(x) QoS You cannot configure QoS on port-channel subinterfaces QoS configuration guide for 9.3(x) QoS […]

LDAPS Problem: Can’t contact LDAP server (-1)

LDAP authentication problem in the customer environment: The error message was received right after entering the password. Tshark says: 1 0.000000000 → TCP 74 44780 → 3269 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=2891116193 TSecr=0 WS=128 2 0.001225814 → TCP 74 3269 → 44780 [SYN, ACK] Seq=0 Ack=1 Win=8192 Len=0 MSS=1460 […]

Linux Routing Memos

These are just small hints and memos what to do on a Debian Linux setup. This is not a complete guide on doing a secured routing environment with Linux. /etc/sysctl.conf: net.ipv4.ip_forward=1 Configure /etc/network/interfaces iptables -t nat -A POSTROUTING -o <upstream_interface> -j MASQUERADE apt-get install iptables-persistent apt-get install iftop apt-get install conntrack conntrack -L -s […]

Zabbix Components and Ports

Zabbix monitoring system consists of components that communicate with each other. Here is a summary of the TCP ports and some configuration characteristics of various connections. Active agent: The Zabbix agent periodically asks the Zabbix proxy (or Zabbix server, if configured to use the server directly) for the list of items that should be collected, […]