I previously wrote a post about the Nexus Roles and how they integrate with a TACACS server.
Cisco Documentation shows the following format to issue multiple roles from a TACACS/RADIUS server.:
We are using Shrubbery TACPLUS, instead of the Cisco ACS software. Last week I noticed that only one role was assigned when multiples should be assigned. Multiple roles are required when using one TACACS server to issue roles for VDC and non-VDC Nexus switches since they need different default User-Roles.
This was tested on a Nexus 5000, a Nexus 7000 and VDC on the same Nexus 7000. Different codes were tried. This was not a NX-OS bug.
Upon further investigation it was obvious, that the syntax above as provided by Cisco was specific their TACACS software, being the ACS software. But I still required multiple Roles to be assigned for my single TACACS configuration to work across multiple Nexus devices. First attempt was the lazy method. Ask uncle Google for any such encounters with a solution. That yielded no practical results. I then contacting Shrubbery for the solution, after that it became clear that possibly nobody else have experienced this problem before.
So the hunt began to find out exactly what was so different in the AAA response from the Cisco ACS software to the TACPLUS software that it did not yield the required results.
Continue reading “Cisco Nexus User Roles using TacPlus”
Memory problems on routers is nothing new. It is generally less of a problem in current day, but is still seen from time to time.
BGP is capable of handling large amount of routes and in comparison to other routing protocols, BGP can be a big memory hog. BGP peering devices, especially full internet peering devices, require larger amounts of memory to store all the BGP routes. Thus it’s not uncommon to see a BGP router run out of memory when a certain route count limit is exceeded.
A router running out of memory, commonly called Low Memory, is always a bad thing. The result of low memory problems may vary from the router crashing, to routing processes being shut down or if you lucky enough erratic behavior causing route flaps and instability in your network. None which is desired.
Low memory can be caused by any of the following:
- Partial physical memory failure.
- Software memory bugs.
- Applications not releasing used memory chunks.
- Incorrect configuration.
- Insufficient memory allocation to a Nexus VDC.
Continue reading “Low Memory Handling”
The Cisco Nexus Series platform has some good things going. Having spent much of my time recently using them, I have come to appreciate some very neat improvements NX-OS is offering over standard IOS. For the most part driving NX-OS is very similar to IOS, but it’s been greatly improved.
One such example is the output from the most used IOS command “show ip int brief”, which on NX-OS only shows ‘IP’ (being layer 3) interfaces. To see the brief state of all types of interfaces use “sh int brief” instead.
N5K-2(config)# sh ip int brief
IP Interface Status for VRF "default"(1)
Interface IP Address Interface Status
Vlan19 10.1.19.6 protocol-up/link-up/admin-up
Vlan22 10.1.22.6 protocol-up/link-up/admin-up
N5K-2(config)# sh int brief
Ethernet VLAN Type Mode Status Reason Speed Port
Interface Ch #
Eth1/1 1 eth trunk up none 1000(D) 51
Eth1/2 22 eth access up none 10G(D) -
Eth1/3 1 eth trunk down SFP not inserted 10G(D) 50
Eth1/4 1 eth trunk down SFP not inserted 10G(D) 50
Eth1/5 1 eth trunk down SFP not inserted 10G(D) -
Eth1/6 19 eth access down SFP not inserted 10G(D) -
Eth1/7 1 eth trunk down Link not connected 10G(D) 5
Eth1/8 1 eth trunk down Link not connected 10G(D) 5
Eth1/9 1 eth fabric down Administratively down 10G(D) 9
Eth1/10 1 eth fabric down FEX identity mismatch 10G(D) 7
Eth1/11 1 eth fabric down vpc peerlink is down 10G(D) 34
Eth1/12 1 eth fabric down SFP not inserted 10G(D) 12
Eth1/13 1 eth fabric up none 10G(D) 15
Eth1/14 1 eth fabric down Administratively down 10G(D) 9
Continue reading “Nexus’ improved CLI”
Ever configured a Nexus switch to use AAA to query a Tacacs+ server? Had some troubles applying standard IOS config to NX-OS?
Possibly if your Tacacs+ server is configured to only allow PAM (Password Authentication Manager) authentication for the users. See when a NX-OS switch sends a AAA authentication packet, by default it is encapsulated using PAP encoding. This is in contrast to normal IOS devices, that use PAM encoding by default.
To illustrate I used the following config:
ip tacacs source-interface mgmt0
tacacs-server host 10.5.0.82 key password
aaa group server tacacs+ TAC
aaa authentication login default group TAC
aaa authorization config-commands default group TAC
aaa authorization commands default group TAC
aaa accounting default group TAC
Continue reading “Nexus defaults to PAP authentication”
November last year, a pair of Cisco Nexus 5010 switches, suddenly started rebooting randomly without user intervention. Since these boxes were a front to a VM environment, stability were of urgent concern. But in order to stabilize the environment, the root cause of the reboots had to be isolated, and quickly.
The Cisco Nexus platform might not be as mature as many would like, but it is quickly becoming a very needed switch in Next-Generation datacenters. Of the things I like most about the Nexus boxes are the readily available local reporting and intuitive system checks. Obviously there are many other features which is making the platform so popular. I’ll cover some of these in time.
Coming back to the rebooting issue. Unlike IOS devices that looses all local logging info, unless a crash dump was saved to NVRAM, the Nexus writes most of its log information to disk. Thus even after the reboot, you have all the information.
Continue reading “Troubleshooting random Nexus reboots”