Understanding int vlan command and general L2 & L3 question

[smk391]

Hi, I'm trying to understand something and thought this was the best place to ask.

I have a 2 Firewall devices, I have a single interface from each device connected to create a virtual interface with an IP address assigned to this interface.  Simple enough, I understand this :) 

the IP is 192.168.1.97/31 for example

It is connected to a switch on the 2 ports, ports 10 & 11. 

These ports don't have an IP addresses assigned directly to them, they are in VLAN 100 , so these are L2 interfaces ?  is this correct ?  So the switch and the FW's are communicating on L2 are they ? 

When I do a show int vlan 100 i see the IP address - 192.168.1.96 /31

Can someone help me understand this, the interfaces are being used for BGP peering according the interface description, I'm more interested in understanding why we have two interfaces in one vlan to communicate with the firewall and why we would do this please. I'll move to understand the BGP config later :) after the basics :)

I know about creating a int vlan interface and how this is used for a SVI interface as a gateway for the L2 devices on the network, but wanted some information on why & the benefits of using two L2 interfaces , this is done for speed and or redundancy?  

Many thanks 

[Mark Malone]

Hi
Without seeing actual configuration or design can only think of this logically

These ports don't have an IP addresses assigned directly to them, they are in VLAN 100 , so these are L2 interfaces ? is this correct ? So the switch and the FW's are communicating on L2 are they ?

Yes the switch ports are in Layer 2 mode , switching traffic up to the firewall , thats standard can be layer 2 or 3 depending what you want and require

Can someone help me understand this, the interfaces are being used for BGP peering according the interface description, I'm more interested in understanding why we have two interfaces in one vlan to communicate with the firewall and why we would do this please. I'll move to understand the BGP config later :) after the basics :)

Most likely some form of physical redundancy between switch and firewall , again depending on config on both ends , but one switch port maybe in blocking mode like active/standby or bundled and both active to firewall for extra throughput

I know about creating a int vlan interface and how this is used for a SVI interface as a gateway for the L2 devices on the network, but wanted some information on why & the benefits of using two L2 interfaces , this is done for speed and or redundancy?

Could be a number of factors , the guy that installed it may be able to answer that better , it could be down to what he knew , or the switch cant support layer 3 , maybe hasn't got the license or cant take a license , cost could of been the issue as l3 licenses are expensive , easier to setup maybe , you can do forms of redundancy with l2 and l3