Nexus FAQ's :
Q. What are the differences between M and F series line cards? What are the differences in F1, F2, F2e and F3 cards?
A. The initial series of line cards launched by cisco for Nexus 7k series switches were M1 and F1. M1 series line cards are basicaly used for all major layer 3 operations like MPLS, OTV, routing etc,however, the F1 series line cards are basically layer 2 cards and used for for FEX, FabricPath, FCoE etc. If there is only F1 card in your chassis, then you can not achieve layer 3 routing. You need to have a M1 card installed in chassis so that F1 card can send the traffic to M1 card for proxy routing. The fabric capacity of M1 line card is 80 Gbps. Since F1 line card dont have L3 functionality, that means you can not use same interface in L3 mode. They are provide a fabric capacity of 230 Gbps.
Later cisco released M2 and F2 series of line cards. A F2 series line card can also do basic Layer 3 functions means you can use interface in L3 mode,however,can not be used for advance L3 feature like OTV or MPLS. M2 line card's fabric capacity is 240 Gbps while F2 series line cards have fabric capacity of 480 Gbps.
The problem with F2 card is that they can not be installed in same vdc with any other card.F2 card has to be in its own vdc.
So, to resolve that, Cisco introduced F2E line cards which can be used with other M series line cards in same VDC. It supports layer 3 but if it is alone in a single vdc. If it is being used with another card, it supports (unlike F2) but then it can be used in L2 mode only.
So, finaly cisco launched F3 cards which are full L3 card. Support all advance layer 3 feature like otv, mpls etc. can be mixed with other cards in same vdc in L2 or L3 mode.
Q. What is Fabric Module? Is it same as line cards?
A. Fabric module are the hardware modules which provides backplane connectivity between I/O modules and SUP. In traditional switches like 6500, the crossbar switch fabric was integrated into chassis and there was no redundancy if crossbar switch fabric is faulty,however, in nexus 7k we have fabric redundancy using switch fabric module.
They are inserted into chassis in the backside and are hot-swappable same as line cards (I/O) modules,however, they dont have any ports on them to connect any external device. So they are not alternatives to line card or I/O modules. You can see them in "show module" command output and they are shown as "X-bar". Nexus 7010 and 7018 can have upto 5 fab modules.
Q. What is fabric module capacity?
A. There are two series of Fabric modules, FAB1 and FAB2.
Each FAB1 has a maximum throughput of 46Gbps per slot meaning the total per slot bandwidth available when chassis is running on full capacity, ie. there are five FAB1s in a single chassis would be 230Gbps. Each FAB2 has a maximum throughput of 110Gbps/slot meaning the total per slot bandwidth available when there are five FAB2s in a single chassis would be 550Gbps. These are the FAB module capacity,however, the actual throughput from a line card is really dependent on type of line card being used and the fabric connection of the linecard being used.
Q. Does a Nexus 2k has an operating system (OS)?
A. No, nexus 2k or fex is a dumb device. It doesnt have any PRE-INSTALLED operating system on it. It can be used with its parent Nexus 5k or 7k switch. When connected to its parent switch, it downloads the operating system from parent switch only.
Q. What is difference between shared mode vs dedicated mode
A. explained in : Shared vs Dedicated mode of ports in Nexus 7k
Q. Can we connect a Nexus 2k to Nexus 7k?
A. Yes,however, not on every line card. There are few line cards which supports Fex.
Q. Can we connect a Nexus 2k or FEX to two parent switches or it can be controlled or connected by only one switch?
A. Yes, we can connect a fex to two parent switches,however, only 5ks. we CANNOT connect a nexus 2k to two Nexus 7Ks. This is dual-homed FEX design and it is supported.
Q. Can we mix different cards like M1/M2/F1/F2 in same vdc?
A. You can mix all cards in same vdc EXCEPT F2 card. The F2 card has to be on it's own VDC. You can't mix F2 cards with M1/M2 and F1 in the same VDC. As per cisco, its a hardware limitation and it creates forwarding issues.
Q. Can we do a redistribute in ospf without a route-map?
A. No, a route-map is required in NX-os while redistributing.
Q. What are the differences between VPC and VSS
A. Explained in: VSS vs VPC (difference between VSS and vPC)
Q. What is VDC
A. Explained in detail: VDC Overview
Q. Can a device in one VDC communicate with device in another VDC?
A. One VDC can not communicate to another VDC over backplane. If a reachability is needed, then we need add a physical connection (via a direct cable or through another switch) between the ports in two seperate VDC's.
Q. Can 3 or more Nexus 7K or 5Ks become vPC Peers?
A. No,you can have only two devices as vPC peers. Each device can serve as a vPC peer to only one other vPC peer.
Q. What are the difference between vPC-peer link and vPC keep-alive link?
A. vPC-peer link is a layer 2 link that is used to check the consistancy parameters,states and config sync and traffic flow(in some cases only). vpc keep-alive link is L3 reachability which is used to check the peer status and role negotiation. Role negotiation happens at the initial stage only. vpc keep-alive link must be setup first in order to bring vpc up. vPC peer link will not come up unless the peer-keepalive link is already up and running.
Q. What are the vpc keep-alive link timers?
A. The default interval time for the vPC peer-keepalive message is 1 second. This is configurable between 400 milliseconds and 10 seconds.You can configure a hold-timeout value with a range of 3 to 10 seconds; the default hold-timeout value is 3 seconds.
Q. How many VDC’s can the Nexus 7000 support?
A. It depends on which SUP you are using:
4 VDCs with SUP1,
4+1 (1 VDC for management) SUP2;
8 + 1 (management) VDC’s with SUP2E.
Q. On a Nexus 7k, when trying to perform a 'no shut' on Ethernet 1/3,the ERROR: Ethernet1/3: Config not allowed, as first port in the port-grp is dedicated error message is received.
A. Explained in details: Shared vs Dedicated mode of ports in Nexus 7k
Q. What are the differences between M and F series line cards? What are the differences in F1, F2, F2e and F3 cards?
A. The initial series of line cards launched by cisco for Nexus 7k series switches were M1 and F1. M1 series line cards are basicaly used for all major layer 3 operations like MPLS, OTV, routing etc,however, the F1 series line cards are basically layer 2 cards and used for for FEX, FabricPath, FCoE etc. If there is only F1 card in your chassis, then you can not achieve layer 3 routing. You need to have a M1 card installed in chassis so that F1 card can send the traffic to M1 card for proxy routing. The fabric capacity of M1 line card is 80 Gbps. Since F1 line card dont have L3 functionality, that means you can not use same interface in L3 mode. They are provide a fabric capacity of 230 Gbps.
Later cisco released M2 and F2 series of line cards. A F2 series line card can also do basic Layer 3 functions means you can use interface in L3 mode,however,can not be used for advance L3 feature like OTV or MPLS. M2 line card's fabric capacity is 240 Gbps while F2 series line cards have fabric capacity of 480 Gbps.
The problem with F2 card is that they can not be installed in same vdc with any other card.F2 card has to be in its own vdc.
So, to resolve that, Cisco introduced F2E line cards which can be used with other M series line cards in same VDC. It supports layer 3 but if it is alone in a single vdc. If it is being used with another card, it supports (unlike F2) but then it can be used in L2 mode only.
So, finaly cisco launched F3 cards which are full L3 card. Support all advance layer 3 feature like otv, mpls etc. can be mixed with other cards in same vdc in L2 or L3 mode.
Q. What is Fabric Module? Is it same as line cards?
A. Fabric module are the hardware modules which provides backplane connectivity between I/O modules and SUP. In traditional switches like 6500, the crossbar switch fabric was integrated into chassis and there was no redundancy if crossbar switch fabric is faulty,however, in nexus 7k we have fabric redundancy using switch fabric module.
They are inserted into chassis in the backside and are hot-swappable same as line cards (I/O) modules,however, they dont have any ports on them to connect any external device. So they are not alternatives to line card or I/O modules. You can see them in "show module" command output and they are shown as "X-bar". Nexus 7010 and 7018 can have upto 5 fab modules.
Q. What is fabric module capacity?
A. There are two series of Fabric modules, FAB1 and FAB2.
Each FAB1 has a maximum throughput of 46Gbps per slot meaning the total per slot bandwidth available when chassis is running on full capacity, ie. there are five FAB1s in a single chassis would be 230Gbps. Each FAB2 has a maximum throughput of 110Gbps/slot meaning the total per slot bandwidth available when there are five FAB2s in a single chassis would be 550Gbps. These are the FAB module capacity,however, the actual throughput from a line card is really dependent on type of line card being used and the fabric connection of the linecard being used.
Q. Does a Nexus 2k has an operating system (OS)?
A. No, nexus 2k or fex is a dumb device. It doesnt have any PRE-INSTALLED operating system on it. It can be used with its parent Nexus 5k or 7k switch. When connected to its parent switch, it downloads the operating system from parent switch only.
Q. What is difference between shared mode vs dedicated mode
A. explained in : Shared vs Dedicated mode of ports in Nexus 7k
Q. Can we connect a Nexus 2k to Nexus 7k?
A. Yes,however, not on every line card. There are few line cards which supports Fex.
Q. Can we connect a Nexus 2k or FEX to two parent switches or it can be controlled or connected by only one switch?
A. Yes, we can connect a fex to two parent switches,however, only 5ks. we CANNOT connect a nexus 2k to two Nexus 7Ks. This is dual-homed FEX design and it is supported.
Q. Can we mix different cards like M1/M2/F1/F2 in same vdc?
A. You can mix all cards in same vdc EXCEPT F2 card. The F2 card has to be on it's own VDC. You can't mix F2 cards with M1/M2 and F1 in the same VDC. As per cisco, its a hardware limitation and it creates forwarding issues.
Q. Can we do a redistribute in ospf without a route-map?
A. No, a route-map is required in NX-os while redistributing.
Q. What are the differences between VPC and VSS
A. Explained in: VSS vs VPC (difference between VSS and vPC)
Q. What is VDC
A. Explained in detail: VDC Overview
Q. Can a device in one VDC communicate with device in another VDC?
A. One VDC can not communicate to another VDC over backplane. If a reachability is needed, then we need add a physical connection (via a direct cable or through another switch) between the ports in two seperate VDC's.
Q. Can 3 or more Nexus 7K or 5Ks become vPC Peers?
A. No,you can have only two devices as vPC peers. Each device can serve as a vPC peer to only one other vPC peer.
Q. What are the difference between vPC-peer link and vPC keep-alive link?
A. vPC-peer link is a layer 2 link that is used to check the consistancy parameters,states and config sync and traffic flow(in some cases only). vpc keep-alive link is L3 reachability which is used to check the peer status and role negotiation. Role negotiation happens at the initial stage only. vpc keep-alive link must be setup first in order to bring vpc up. vPC peer link will not come up unless the peer-keepalive link is already up and running.
Q. What are the vpc keep-alive link timers?
A. The default interval time for the vPC peer-keepalive message is 1 second. This is configurable between 400 milliseconds and 10 seconds.You can configure a hold-timeout value with a range of 3 to 10 seconds; the default hold-timeout value is 3 seconds.
Q. How many VDC’s can the Nexus 7000 support?
A. It depends on which SUP you are using:
4 VDCs with SUP1,
4+1 (1 VDC for management) SUP2;
8 + 1 (management) VDC’s with SUP2E.
Q. On a Nexus 7k, when trying to perform a 'no shut' on Ethernet 1/3,the ERROR: Ethernet1/3: Config not allowed, as first port in the port-grp is dedicated error message is received.
A. Explained in details: Shared vs Dedicated mode of ports in Nexus 7k
great post. helped a lot. Thanks for putting
ReplyDeleteNice questions and answers sir, Thank you.
ReplyDeleteNice, if only Cisco documentation was this straight forward!
ReplyDeletehelped lot great post.........
ReplyDeleteNice Post. Please tell us the difference between M1/M2 and F1/F2 cards.
ReplyDeleteNice FAQs.... Helped me a lot.. Thanks
ReplyDeleteExcellent Post. Very Very helpful. great Work!!!!
ReplyDeleteNeed some help with NTP we have a admin vdc and we use vdc 2 for clock sync however the NTP config on vdc 2 is accepted and shown in the show run we are not able to see the configured NTP servers are in sync state .. any ideas
ReplyDeleteGreat explanation
ReplyDeleteVery nice information. Appreciate it
ReplyDelete