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Parsing BGP packets using tcpdump

We should use tcpdump tool to read BGP routing messages, of course, several ways are available.

Capturing BGP packets on the fly

tcpdump -i eth0 tcp proto 179

where BGP ip protocol number is 89, and the protocol field is the 9th octet on the ip header.

BGPv4 - open and keepalive messages - moving from connect to open state - eBGP peers

Description

Routers R1 nad R2 are connected through the serial HDLC line. R1 router is a BGP speaker running AS 200, the R2 router is an AS100 BGP speaker. Both routers are configured with correct BGP neighbor commands to form an eBGP peering. The capture is displaying the moment when we activate serial interconnecting interface (no shutdown)  of the R2 router.

EIGRP - deleting route - query/reply

Description

EIGRP - an update

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.

Topology

|----FA0/0-(192.168.1.1/24)----|R1|----s0/0----(1.0.0.0/30)----s0/0----|R2|----Fa0/0-(192.168.2.1/24)----|

EIGRP - forming adjacency and initial update

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).

Topology

|----FA0/0-(192.168.1.1/24)----|R1|----s0/0----(1.0.0.0/30)----s0/0----|R2|----Fa0/0-(192.168.2.1/24)----|

Number of packets: 15

How to save an open file from web browser directly to GoogleDocs

How to clear an ASA startup configuration

If we have access to config mode we may type

config t
configure factory-default

 

Enabling default Telnet client on Windows 7 operating system

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:

 

1) Open Control Panel and choose Programs and Features

2) From the left meny choose "Turn windows features on or off"

 

IGMPv2 packet capture

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

Configuring simple MPLS network

Objective

Create a simple MPLS network and observe partial parts of MPLS functionality. MPLS network consist of four routers, two edge routers - LSE1 and LSE2 whose fastEthernet interfaces are not parts of the MPLS network and two Label Switch Routers - LSR1 and LSR2 interconnected through serial lines.

Topology

Four routers are connected in a chain line topology:

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