In many setups Kamailio is used as a PROXY server that takes care of routing calls to servers providing voice services, e.g. voicemail, IVR or conference calls.
There are a few things an administrator must keep in mind.
Sometimes we need to capture and parse OSPF packets for next analysis and we have a comand line only, in my case on linux server with dynamips. We should use tcpdump tool for this purpose, of course, several ways are available.
Capturing OSPF packets on the fly
We investigate a special topology condition, where a switch is connected itself on ports Faa0/1 and Fa0/2, and one of the port has BPDUFilter feature applied (i.e. simulating STP is switched off). Both ports are in the same vlan (vlan 1 here). The question is: Is there a topology loop?
Initial state
One of firefox features is that when typing a partial URL into the URL field (URL or location bar), Firefox will automatically contact Google's search engine to find and provide search answers. This work fine till one of your computer users download the Yahoo search add-ons, which makes Yahoo Search! default Firefox search without being aware or alerted about that. So if we have the Yahoo add-on and we will type a key word (or partial Web address), we will not go straight to the Google search but instead we will see Yahoo Search results.
The capture is showing the q-in-q tagging where VLAN ID 600 is the customer VLAN and VLAN ID 101 is the metro tag (Service provider tag). Tha capture consist of ICMP pings among two customer IP hosts (vlan 600) with IP addresses, 192.168.1.1 and 192.168.1.2, carried over ISP MAN network (service ID 101).
Number of packets: 11
The capture displays an IGMPv2 multicast communication. The IP host with the IP address 192.168.10.108 is wishing to join 233.10.47.43 multicast group sending the Memership Report IGMP message (1st and 2nd packet). After sucesfull joining, it is leaving the group after a while with IGMP Leave Group message (3td packet), which follows by two Membership Queries issued by the default gateway with IP 192.168.10.1 on the multicast group address (233.10.47.43) checking for the actual group membership on the LAN for the multicast group.
Number of packets: 5
In our Cisco NetAcad classes we had utilized built in Windows telnet client (of course we have putty instead), which was available in each system till Windows XP by default. In windows 7 the telnet client is not available by default, but we simply may do it available in few simple following steps:
If we have access to config mode we may type
config t configure factory-default
Description
Routers R1 nad R2 are connected through serial HDLC line. The capture is displaying a moment when we activate EIGRP routing (AS 1) on the serial line between both routers only (R1 was first). Capture displays the Hello packet exchange following with Update packets with an empty body (IP TLV).
Description
Routers R1 nad R2 are connected through the serial HDLC line. The capture is displaying a moment when we activate EIGRP routing (AS 1) for the fastethernet interface of the R2 router. Capture displays the exchange of Update packet with information about the fastEthernet network address (192.168.2.0) immediatelly followed by the Ack EIGRP packet emitted by R1 to confirm receipt.