IP routing command in Cisco Catalyst 9300

[nips]

Hi All,

I have experienced in Cisco 9300 switch without the IP routing command, the default route is functioning but the specific static routes not functioning. But the routes are adding to the configuration and the routing table. Could you explain the exact use of IP routing and the actual effect of use it in Cisco 9300 switch which has Network-Essential license?

[MHM Cisco World]

Do show run all<<- to see if command run or not.

I think command run by defualt in some SW.

[nips]

Executed the show run all command and not found the ip routing enabled. Without the ip routing enabled, when pinged the remote server in Site B connected to a C9300 switch, from the Site A switch (C9300),not worked. But ping worked to the SVI of the same segment on the switch in Site B. Only Enabling IP routing ping to the server worked. Static Routes have been configured for this communication on a L2 VPN link. I can understand this without Ip routing command static routes are not functioning. But my concern is why the default route which was configured early for the management purpose worked without the IP routing command?

[MHM Cisco World]

there are two traffic mgmt and Data and below table show which traffic pass with which command 

                         mgmt traffic             Data traffic (user traffic)
default GW           Yes                               NO
default route         Yes                              Yes

in End you must consider SW (without ip routing) like any host need GW to send traffic to any IP outside it mgmt SVI subnet

https://www.cisco.com/c/en/us/support/docs/ip/routing-information-protocol-rip/16448-default.html

[Flavio Miranda]

@nips 

 with Essential license you should be enable to do routing on the switch.  If you run the command "ip routing" and you can not see the command on the show running-conf, something is not right with the switch.

 Default routing will always be allowed, even in layer2 only switch.

Can I see the output of "show version" , show license and show running-confg ?

[Richard Burts]

Would you post the output for these commands:

show run all | include routing

show run all | include default

show ip route

[ThomasCampbell64]

IP routing command essentially turns the switch from a Layer 2 Switch to a Layer 3 switch.

Layer 2 switches still use default-gateway in order to be able to manage the device in the network however if "ip routing" is enabled this still allows for management of the switch however with Layer 3 IP routing capabilities such as SVI and routing protocols such as OSPF and EIGRP.

[balaji.bandi]

IP routing is disabled on the device by default, and you must enable it before routing occurs.

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9300/software/release/17-3/configuration_guide/rtng/b_173_rtng_9300_cg/configuring_ip_unicast_routing.html

If the Uplink device is doing the routing part, you should be able to use the default gateway if this switch is acting as Layer 2 only. If the switch needs to process inter-vlan routing, then you need to enable IP routing to work as expected. In theory and technically, you need to replace the default gateway with the IP routing x.x.x x.x.x command.

[paul driver]

Hello

---

@nips wrote:

Hi All,

I have experienced in Cisco 9300 switch without the IP routing command, the default route is functioning but the specific static routes not functioning. But the routes are adding to the configuration and the routing table. Could you explain the exact use of IP routing and the actual effect of use it

---

Without ip routing enabled on a switch then that switch is a host switch, it performs no routing whatsoever. just L2 switching functions its basically just like your pc at home, it has a ip address/subnet mask /default gateway. = A host device

Its own ip addressing is ONLY used for management reachablilty to itself so any device on the same vlan segment will be able to reach it, and with a default-gateway applied devices off its own vlan can reach it also 

Its default-gateway ip  will be another the L3 device on the network that is performing the ip routing not just for this L2 host switch vlan but no doubt for other routing segments ( again just like your pc at home)


When you enable ip routing then the switch now becomes a L3 device in its own right  (just like a router) , as such it own default-gateway is meaningless as now the L3 switch is performing routing functions like route lookups and making forwarding decisions and to do this it requires routing information be it in the form of statically applied routes or dynamically learned routes from a routing process (eigrp/ospf/isis and maybe even bgp)

[nips]

Hi All,

With further studying and troubleshooting of the setup understood the below.

• For functioning Static routes (there is a limit for static route count) and Default route no need to run "ip routing" command. 
• For the inter-vlan routing need to run "ip routing" command. But within the switch its own SVI IPs are reachable. But without "ip routing" command there is no  Host to Host reachability between two VLAN segments.

Now the last concern I have is when the Network-Advantage license is enabled on the switch do we need to run "ip routing" command for functioning dynamic routing protocols too ?

[MHM Cisco World]

• For the inter-vlan routing need to run "ip routing" command. But within the switch its own SVI IPs are reachable. But without "ip routing" command there is no  Host to Host reachability between two VLAN segments. Correct but that not what you ask in your OP
  
  
• For functioning Static routes (there is a limit for static route count) and Default route no need to run "ip routing" command. Not Correct you need ip routing. MHM

[nips]

Understanding "without "ip routing" command, static routes are not functioning" is my bad. @MHM Cisco World  and all thanks for your replies

[MHM Cisco World]

You are so welcome friend 

Keep ask

Have a nice day 

MHM