Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.14.1.0 - Page 229

Capturing PDUs To capture incoming and outgoing PDUs on a per-peer basis, use the capture bgp-pdu neighbor direction command. To disable capturing, use the no capture bgp-pdu neighbor direction command. The buffer size supports a maximum value between 40 MB (the default) and 100 MB. The capture buffers are cyclic and reaching the limit prompts the system to overwrite the oldest PDUs when new ones are received for a given neighbor or direction. Setting the buffer size to a value lower than the current maximum, might cause captured PDUs to be freed to set the new limit. NOTE: Memory on RP1 is not pre-allocated and is allocated only when a PDU needs to be captured. The buffers storing the PDU free memory when: • BGP is disabled. • A neighbor is unconfigured. • The clear ip bgp command is issued. • New PDU are captured and there is no more space to store them. • The max buffer size is reduced. (This may cause PDUs to be cleared depending on the buffer space consumed and the new limit.) Examples of the show capture bgp-pdu neighbor Command To change the maximum buffer size, use the capture bgp-pdu max-buffer-size command. To view the captured PDUs, use the show capture bgp-pdu neighbor command. DellEMC#show capture bgp-pdu neighbor 20.20.20.2 Incoming packet capture enabled for BGP neighbor 20.20.20.2 Available buffer size 40958758, 26 packet(s) captured using 680 bytes PDU[1] : len 101, captured 00:34:51 ago ffffffff ffffffff ffffffff ffffffff 00650100 00000013 00000000 00000000 419ef06c 00000000 00000000 00000000 00000000 00000000 0181a1e4 0181a25c 41af92c0 00000000 00000000 00000000 00000000 00000001 0181a1e4 0181a25c 41af9400 00000000 PDU[2] : len 19, captured 00:34:51 ago ffffffff ffffffff ffffffff ffffffff 00130400 PDU[3] : len 19, captured 00:34:51 ago ffffffff ffffffff ffffffff ffffffff 00130400 PDU[4] : len 19, captured 00:34:22 ago ffffffff ffffffff ffffffff ffffffff 00130400 [. . .] Outgoing packet capture enabled for BGP neighbor 20.20.20.2 Available buffer size 40958758, 27 packet(s) captured using 562 bytes PDU[1] : len 41, captured 00:34:52 ago ffffffff ffffffff ffffffff ffffffff 00290104 000100b4 14141401 0c020a01 04000100 01020080 00000000 PDU[2] : len 19, captured 00:34:51 ago ffffffff ffffffff ffffffff ffffffff 00130400 PDU[3] : len 19, captured 00:34:50 ago ffffffff ffffffff ffffffff ffffffff 00130400 PDU[4] : len 19, captured 00:34:20 ago ffffffff ffffffff ffffffff ffffffff 00130400 [. . .] The following example shows how to view space requirements for storing all the PDUs. With full internet feed (205K) captured, approximately 11.8MB is required to store all of the PDUs. DellEMC(conf-router_bgp)#do show capture bgp-pdu neighbor 172.30.1.250 Incoming packet capture enabled for BGP neighbor 172.30.1.250 Available buffer size 29165743, 192991 packet(s) captured using 11794257 bytes [. . .] DellEMC(conf-router_bgp)#do sho ip bg s BGP router identifier 172.30.1.56, local AS number 65056 Border Gateway Protocol version 4 (BGPv4) 229