Let’s say you have a switch.\u00a0 And you are on a computer that is connected to the switch.\u00a0 You know the following:<\/p>\n
But, you’re too lazy to walk over to the data center to figure out which port you’re connected on.<\/p>\n
Here’s what you do (assuming you’re running Red Hat or CentOS)<\/p>\n
yum - y install net-snmp-utils<\/pre>\nThis gives you the snmpwalk command.<\/p>\n
Now:<\/p>\n
first, figure out your MAC address:<\/p>\n
[root@n33 etc]# ifconfig eth0\r\neth0\u00a0\u00a0\u00a0\u00a0\u00a0 Link encap:Ethernet\u00a0 HWaddr 00:A0:D1:E9:3E:DC \u00a0\r\n inet addr:10.3.0.133\u00a0 Bcast:10.3.255.255\u00a0 Mask:255.255.0.0\r\n inet6 addr: fe80::2a0:d1ff:fee9:3edc\/64 Scope:Link\r\n UP BROADCAST RUNNING MULTICAST\u00a0 MTU:1500\u00a0 Metric:1\r\n RX packets:972965 errors:0 dropped:0 overruns:0 frame:0\r\n TX packets:637686 errors:0 dropped:0 overruns:0 carrier:0\r\n collisions:0 txqueuelen:1000\r\n RX bytes:587009797 (559.8 MiB)\u00a0 TX bytes:100870077 (96.1 MiB)\r\n Memory:fcde0000-fce00000<\/pre>\nSo my Mac is 00:A0:D1:E9:3E:DC<\/p>\n
Nice.<\/p>\n
Now lets look for this mac address on the switch.\u00a0 Assuming my community string is ‘foobar’ and my switch is set up to do snmp version 1, and my switch name is switch1, I do:<\/p>\n
snmpwalk\u00a0 -v 1 -c foobar switch1 SNMPv2-SMI::mib-2.17.4.3.1.1<\/pre>\nWhen you do this, you’ll see a list of the nodes.\u00a0 Among them should be a Hex-STRING that matches your MAC address:<\/p>\n
...\r\nSNMPv2-SMI::mib-2.17.4.3.1.1.0.160.209.233.62.220 = Hex-STRING: 00 A0 D1 E9 3E DC\r\n...<\/pre>\nNotice that the string:<\/p>\n
0.160.209.233.62.220<\/pre>\nIs the decimal representation of the MAC address:<\/p>\n
00:A0:D1:E9:3E:DC<\/pre>\nSo you have verified one important piece of information:\u00a0 You are in fact connected on this switch!<\/p>\n
Now figure out which port!<\/p>\n
We use the decimal representation of the MAC address from this point on to find the port.\u00a0 Usually for me this works:<\/p>\n
snmpwalk -v 1 -c foobar switch1 SNMPv2-SMI::mib-2.17.7.1.2.2.1.2<\/pre>\nAmong the output I get:<\/p>\n
SNMPv2-SMI::mib-2.17.7.1.2.2.1.2.413.0.160.209.233.62.220 = INTEGER: 5<\/pre>\nThis tells me that my node is connected to port 5 on the switch.<\/p>\n
Sometimes (on cisco switches and others) you may need to use a different approach for the mac-to-index values:<\/p>\n
snmpwalk -v 1 -c foobar switch1 SNMPv2-SMI::mib-2.17.4.3.1.2<\/pre>\nThis is great, in that I never had to leave my chair to figure this out!\u00a0 The pounds pile up and my largeness increases.\u00a0 Anybody got a better\/easier way to do this?<\/p>\n","protected":false},"excerpt":{"rendered":"
Let’s say you have a switch.\u00a0 And you are on a computer that is connected to the switch.\u00a0 You know the following: The name of the switch The SNMP community string and version the switch uses. But, you’re too lazy to walk over to the data center to figure out which port you’re connected on….<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[920],"tags":[62,63,61],"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/benincosa.com\/index.php?rest_route=\/wp\/v2\/posts\/155"}],"collection":[{"href":"https:\/\/benincosa.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/benincosa.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/benincosa.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/benincosa.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=155"}],"version-history":[{"count":4,"href":"https:\/\/benincosa.com\/index.php?rest_route=\/wp\/v2\/posts\/155\/revisions"}],"predecessor-version":[{"id":2822,"href":"https:\/\/benincosa.com\/index.php?rest_route=\/wp\/v2\/posts\/155\/revisions\/2822"}],"wp:attachment":[{"href":"https:\/\/benincosa.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=155"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/benincosa.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=155"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/benincosa.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=155"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}