Using CDP to understand Data ONTAP networking

Have you ever been on a Data ONTAP system without a clear idea of how the physical network is connected, and wish you could interrogate your network to try and find out? If so, CDP – the Cisco Discovery Protocol – might be the help you’re looking for. This can be very useful on systems with large or complex Ethernet configurations. Once CDP is enabled in Data ONTAP, your Cisco switches will become aware of which NetApp systems are cabled to which ports. It’ll know both the source port (on the NetApp) and the destination port (on the Cisco).

CDP is supported in both 7-mode and cDOT, and is simply enabled with an option command.

To enable CDP in 7-mode:

options cdpd.enable on

To enable CDP in cDOT:

node run -node * options cdpd.enable on

The nice thing about NetApp’s CDP implementation is that it’s bi-directional. That means you can query CDP from either the Cisco switch or the NetApp controller and see information — meaning you don’t have to rely on a network administrator to provide you the information.

To view CDP information from 7-mode Data ONTAP, you would use the cdpd show-neighbors command.

Here’s some sample output:

mystic> cdpd show-neighbors
Local  Remote          Remote                 Remote           Hold  Remote    
Port   Device          Interface              Platform         Time  Capability
------ --------------- ---------------------- ---------------- ----- ---------- 
e0M    charles         e0M                    FAS3170           146   H         
e0M    nane-cat4948-sw GigabitEthernet1/8     cisco WS-C4948-.  174   RSI       
e3a    nane-nx5010-sw. Ethernet1/4            N5K-C5010P-BF     173   SI        
e4a    nane-nx5010-sw. Ethernet1/14           N5K-C5010P-BF     177   SI

Note that we can see that Filer’s HA partner, charles, in the output. Here we can see that e0M is cabled to port Giga1/8 on nane-cat4948, whereas e3a and e4a are cabled to Eth1/4 and Eth1/14 on nane-nx5010-sw respectively.

This is incredibly useful information if you’re ever trying to track down how a system is cabled!

And from clustered Data ONTAP, to view CDP neighbor information you would use the run -node nodeName cdpd show-neighbors command.

The output is the same format as in 7-mode:

dot83cm::> node run -node local cdpd show-neighbors
Local  Remote          Remote                 Remote           Hold  Remote    
Port   Device          Interface              Platform         Time  Capability
------ --------------- ---------------------- ---------------- ----- ---------- 
e6a    nane-nx5010-sw. Ethernet1/12           N5K-C5010P-BF     145   SI        
e6b    nane-nx5010-sw. Ethernet1/5            N5K-C5010P-BF     145   SI        
e4a    dot83cm-01      e4a                    FAS3240           161   H         
e4b    dot83cm-01      e4b                    FAS3240           161   H         
e0a    nane-cat4948-s. GigabitEthernet1/9     cisco WS-C4948-.  168   RSI

In this case, e6a and e6b go to the same switch, with e4a and e4b going to the other node in this HA pair — that’s my switchless cluster interconnect. e0a goes to an older Catalyst switch.

And to view CDP information from Cisco IOS or NX-OS, you would use the show cdp neighbors command.

Some sample output:

nane-nx5010-sw# show cdp neighbors
Capability Codes: R - Router, T - Trans-Bridge, B - Source-Route-Bridge
                  S - Switch, H - Host, I - IGMP, r - Repeater,
                  V - VoIP-Phone, D - Remotely-Managed-Device,
                  s - Supports-STP-Dispute, M - Two-port Mac Relay

Device ID              Local Intrfce   Hldtme  Capability  Platform      Port ID
US-WLM-LS02            mgmt0           124     R S I       WS-C6509      Gig5/1 
nane-cat4948-sw        Eth1/2          179     R S I       WS-C4948-10GE Ten1/49
dot83cm-01             Eth1/3          163     H           FAS3240       e6b    
mystic                 Eth1/4          127     H           FAS3170       e3a    
dot83cm-02             Eth1/5          158     H           FAS3240       e6b

More detailed information about the output of CDP commands can be found in the relevant Network Management Guide, which are linked below. CDP has been supported since Data ONTAP 8.0.

In IOS/NX-OS, you may wish to run show cdp neighbors detail to gather more information.



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