• Guest shell and the host Bash Shell use Kernel Stack (kstack).

• The Guest Shell and the host Bash Shell start in the default network namespace.

  • Use the setns system call to access other network namespaces

  • The nsenter and ip netns exec utilities can be used to execute within the context of a different network namespace.

• The interface state may be read from /proc/net/dev or retrieved using other typical Linux utilities such as ip , ifconfig , or netstat . The counters are for packets that have initiated or terminated on the switch.

• Use ethtool –S to get extended statistics from the net devices, which include packets that are switched through the interface.

• You can run packet capture applications like tcpdump to capture packets that initiate or terminate on the switch.

• There is no support for networking state changes (interface creation or deletion, IP address configuration, MTU change, and so on) from the Guest Shell.

• IPv4 and IPv6 are supported.

• Raw PF_PACKET is supported.

• Only on stack (Netstack or kstack) at a time can use well-known ports (0-15000), regardless of the network namespace.

• There is no IP connectivity between applications using Nestack and applications running kstack on the same switch. This limitation holds true regardless of whether the kstack applications are being run from the host Bash Shell or within a container.

• Applications within the Guest Shell are not allowed to send packets directly over an Ethernet out-of-band channel (EOBC) interface to communicate with the line cards or standby Sup.

• The management interface (mgmt0) is represented as eth1 in the kernel netdevices.

Netdevices representing the front channel port interfaces are always in the ADMIN UP state. The final, effective state is determined by the link carrier state.

The following example shows the following interfaces in NX-OS, where eth1/17 is shown as up and eth1/1 is shown as down:

root@kstack-switch# sh int ethernet 1/17 brief
Eth1/17       --      eth  routed up      none                       1000(D) –

root@kstack-switch# sh int ethernet 1/1 brief
Eth1/1        --      eth  routed down    Link not connected         auto(D) –

The following example shows these same interfaces, but this time as shown in the Bash shell using the ip link show command:

bash-4.3# ip link show Eth1-17
49: Eth1-17: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 100
    link/ether 00:42:68:58:f8:eb brd ff:ff:ff:ff:ff:ff

bash-4.3# ip link show Eth1-1
33: Eth1-1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN mode DEFAULT group default qlen 100
    link/ether 00:42:68:58:f8:eb brd ff:ff:ff:ff:ff:ff

In this example, Eth1-1 is shown as being UP, but is shown as NO-CARRIER and state DOWN.

The following example shows these same interfaces, but this time as shown in the Bash shell using the ifconfig command:

bash-4.3# ifconfig Eth1-17
Eth1-17   Link encap:Ethernet  HWaddr 00:42:68:58:f8:eb
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:7388 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          RX bytes:0 (0.0 B)  TX bytes:1869164 (1.7 MiB)

bash-4.3# ifconfig Eth1-1
Eth1-1    Link encap:Ethernet  HWaddr 00:42:68:58:f8:eb
          inet addr:99.1.1.1  Bcast:99.1.1.255  Mask:255.255.255.0
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

The output from the ifconfig command provides different information, where the RUNNING keyword is used to represent the final state. By default, all netdevices show the keyword UP, which represents the ADMIN state of the netdevice in the kernel.

The following IPv4 and IPv6 behaviors are applicable to netdevices configured on the switch:

• IPv4 address on netdevices — The IPv4 addresses are plumbed to the kernel space only when the interface is in the UP state. Once plumbed, the IPv4 address continues to stay with the netdevice in the kernel even if the interface goes DOWN. It will be removed only after you have entered the following CLI command to explicitly remove the IP address from the NX-OS interface:

  Interface Eth1/1
              no ip address IP-address
  
  

• IPv6 address on netdevices — Netdevices are always in the Admin UP state, so the IPv6 addresses will not get flushed from the kernel when the interface goes down.