Menu
Jump to Configuring VLAN Interfaces - Where the number is between 1 and 4090. Hostname(config-if)# no forward interface vlan number. If I understand your design, I think your default route have to be: route outside 0.0.0.0 0.0.0.0 203.1.1.1 1. Share improve this answer.
Hello,I have a FW ASA 5515 and I came accross this article:. It shows that in ASA 5505 it was possible to create VLAN interfaces, and in 5515 that doesn´t seem to be possible anymore (in 5515 only VLAN subinterfaces?). So, my questions are:1) Can I accomplish what was possible in 5505 using the command: no forward interface vlan number? I want to be able to isolate interfaces from each other, for example, interface gigabitEthernet 0/1 should never communicate with interface gigabitEthernet 0/5 regardless if there are ACLs, same security-levels, etc. It seems that with no forward interface vlan command that was what I needed.2) Has the concept of VLANs in 5515 died? I mean, those VLANs that you set in subinterfaces in 5515 are the ones set up in switches and arrive at the FW physical interface through the trunk, then they are directed to the subinterface by their IDs. Are VLANs in ASA5515 only possible (if ever) in transparent mode?3) In fact, 1) is really important to me, so if I´m to use subinterfaces, which I will probably do, can I have configurations at the subinterface level that forbids communication between two subinterfaces or between a subinterface and another physical interface (regardless of ACLs and security-levels)?Thank you. It's worth noting that you dont HAVE to use subinterfaces - if you switch ports are in access mode then you will only set the VLAN on the switch.If however you are using an 802.1q trunked interface (with a switch that can do this) and you want to carry several VLANs to the same physical port on your 5515, this is when you use subinterfaces, to allow the correct traffic to the correct VLAN on the same interface.
In this case, the VLAN is going to be managed by a switch, as the 5515 is not a switch.As mentioned also, to ensure no two segments communicate with eachother, you must ensure you have ACL's set correctly.
We wrote an article which covers as a concept, and another article on. The remaining subject to cover is the different options that exist for routing between VLANs. Why do we need Routing Between VLANs?As we learned in a prior article, VLANs create a between Switch ports. Essentially, each VLAN behaves like a separate physical switch.
To illustrate this, below are two topology pictures of the same environment – one Physical and one Logical.The Physical topology depicts a switch and four hosts in two different VLANs – Host A and Host B are in VLAN 20 and Host C and Host D are in VLAN 30. The logical topology reflects how the physical topology operates – the two VLANs essentially create two separate physical switches. Despite all four hosts being connected to the same physical switch, the logical topology makes it clear that the hosts in VLAN 20 are unable to speak with the hosts in VLAN 30. Notice since there is nothing connecting the two “virtual” switches, there is no way for Host A to speak to Host C.Since Host A and Host C are in different VLANs, it is also implied that they are in different Networks. Each VLAN will typically correspond to its own. In this diagram, VLAN 20 contains the 10.0.20.0/24 network, and VLAN 30 contains the 10.0.30.0/24 network.The purpose of a Switch is to facilitate communication within networks. This works great for Host A trying to speak to Host B.
However, if Host A is trying to speak to Host C, we will need to use another device – one whose purpose is to facilitate communication between networks.If you’ve read the series, then you know that the device which facilitates communication between networks is a.A router will perform the routing function necessary for two hosts on different networks to speak to one another. In the same way, a Router is what we will need in order for hosts in different VLANs to communicate with one another.There are three options available in order to enable routing between the VLANs:.The remainder of this article will explore these three options and their configuration. Router with Separate Physical InterfacesThe simplest way to enable routing between the two VLANs to simply connect an additional port from each VLAN into a Router.The Router doesn’t know that it has two connections to the same switch — nor does it need to. The Router operates like normal when routing packets between two networks.In fact, the process of a packet moving from Host A to Host D in this topology will work exactly as it does in. The only difference is since there is only one physical switch, there will only be one MAC address table – each entry includes the mapping of switchport to MAC address, as well as the VLAN ID number that port belongs to.Each switch port in this diagram is configured as an, we can use the range command to configure multiple ports as once. Switch# show running-config.vlan 20name RED!vlan 30name BLUE.interface Ethernet2/0switchport access vlan 20switchport mode access!interface Ethernet2/1switchport access vlan 20switchport mode access!interface Ethernet2/2switchport access vlan 20switchport mode access!interface Ethernet3/0switchport access vlan 30switchport mode access!interface Ethernet3/1switchport access vlan 30switchport mode access!interface Ethernet3/2switchport access vlan 30switchport mode access.
Switch# show cdp neighborsCapability Codes: R - Router, S - Switch, I - IGMP, B - Source Route Bridge.Device ID Local Intrfce Holdtme Capability Platform Port IDRouter Eth 3/0 152 R B Linux Uni Eth 0/3Router Eth 2/0 166 R B Linux Uni Eth 0/2Router with Sub-InterfacesThe previously described method is functional, but scales poorly. If there were five VLANs on the switch, then we would need five switchports and five router ports to enable routing between all five VLANsInstead, there exists a way for multiple VLANs to terminate on a single router interface. That method is to create a Sub-Interface.A Sub-Interface allows a single Physical interface to be split up into multiple virtual sub-interfaces, each of which terminate their own VLAN.Sub-interfaces to a Router are similar to what are to a Switch – one link carrying traffic for multiple VLANs. Hence, each router Sub-interface must also add a to all traffic leaving said interface.The logical operation of the Sub-interface topology works exactly as the separate physical interface topology in the section before it.
The only difference is with Sub-interfaces, only one Router interface is required to terminate all VLANs.Keep in mind, however, that the drawback with all VLANs terminating on a single Router interface is an increased risk of congestion on the link.The Sub-interface feature is sometimes referred to as Router on a Stick. This is in reference to the single router terminating the traffic from each VLAN.The Switch’s port facing the router is configured as a standard. A point of clarity regarding the Sub-interface syntax. The number after the physical interface (fa0/3.20 and fa0/3.30) simply serves the purpose of splitting up the physical interfaces into Sub-interfaces. The number specified in the encapsulation dot1q vlan ## command is what actually specifies what VLAN ID# the traffic belongs to.These two values do not have to match, but often they do for the purpose of technician sanity.Below you will find various show commands for the Router and the Switch. These can be used to understand and validate how the environment is functioning.
![No Forward Interface Vlan 1 No Forward Interface Vlan 1](http://2.bp.blogspot.com/-uHZJbgDz2sg/Tne9be5js3I/AAAAAAAAAZk/Q2A8MUhl3nY/w1200-h630-p-k-no-nu/Router_tradicional_1.jpeg)
Router Sub-Interface Show Commands. Switch# show cdp neighborsCapability Codes: R - Router, S - Switch, I - IGMP, B - Source Route Bridge.Device ID Local Intrfce Holdtme Capability Platform Port IDRouter Eth 1/1 136 R B Linux Uni Eth 1/1Layer 3 SwitchThe last option for routing between VLANs does not involve a router at all. Nor does it involve using a traditional switch.Instead, a different device entirely can be used. This device is known as a Layer 3 Switch (or sometimes also as a Multilayer switch). But exactly what is a Layer 3 switch?A Layer 3 Switch is different from a traditional Layer 2 Switch in that it has the functionality for routing between VLANs intrinsically. In fact, when considering how a L3 Switch operates, you can safely imagine that a Layer 3 Switch is a traditional switch with a built in Router.With regard to VLANs the Multilayer switch is configured mostly the same way as a regular L2 switch.
MultilayerSwitch(config)# interface vlan 20MultilayerSwitch(config-if)# ip address 10.0.20.1 255.255.255.0MultilayerSwitch(config-if)# no shutdownMultilayerSwitch(config)# interface vlan 30MultilayerSwitch(config-if)# ip address 10.0.30.1 255.255.255.0MultilayerSwitch(config-if)# no shutdownThe two configurations above will enable routing between VLAN 20 and VLAN 30. The hosts in each VLAN can use the IP addresses 10.0.20.1 and 10.0.30.1 as their default gateway (respectively).When Host A sends a packet to Host B, the packet will be switched within the same VLAN – no L3 processing will occur.When Host A sends a packet to Host C, the packet will be sent to the SVI to be routed to the other VLAN – all regular L3 processing will occur: the TTL will be decremented. Multilayer Switch Configuration. Note: both sets of tabs and configuration above are from the same device. For the sake of organization, one set of tabs refer to the L3 functions and the other refers to the L2 functions.SummaryThis article discussed the three different options for Routing between VLANs.
In each case, the hosts in communication behave exactly the same. In fact, the hosts have no visibility into how and what they are connected to.Each strategy above has its own benefits and limitations. Hopefully at this point you have a good idea of the options available to enable communication between hosts on different VLANs. Hi Vishal, absolutely!Host A has the IP address 10.0.20.11 and Host C has the IP address 10.0.30.33. These IP address will be the Source and Destination in the L3 header. Remember, L3 is responsible for, therefore this header will not change.To understand the L2 header, we’ll have to take a look at the.
From the show arp command (the arp tab) we learn the four MAC addresses that will be used in the process:Host A has a MAC address of 0050.7966.6800, and Host C has a MAC address of 0050.7966.6803. AndThe MAC address of SVI 20 is aabb.cc80.0200, and the MAC address of SVI 30 is aabb.cc80.0200 (it is common for all SVIs on a L3 switch to share the same MAC address).That said, when the packet is just leaving Host A, the L2 source will be 0050.7966.6800, and the L2 destination will be aabb.cc80.0200. When the packet is just leaving SVI 30, the L2 source will be aabb.cc80.0200, and the L2 destination will be 0050.7966.6803.L2 will accomplish the delivery to.Hope this helps. Perfect, just one suggestion: It would be perfect to add also “show cdp neigh detail” to your article, because it would be very explanatory to see the output on switch (in the first scenario – router with sub-interfaces), how are IP addresses visible in the output. Also if L3 switch would have one access switch connected to it, it would be perfect to see “sh cdp neigh detail” on this access switch, how are IP addresses visible in the output. If someone know the answer, please post it:).There is another problem to discussion, what with the native vlan, and when, why and where to change configuration for that (router – switch, L3switch – L2switch).
A host can not always be trusted to do the right thing. =)Look at the output of “show mac-address table” in. Host A has the MAC address 0050.7966.6800 and is in VLAN 20. Host D is in VLAN 30 and has the MAC address 0050.7966.6803. Being that these hosts are in different VLANs, we do NOT want them to speak directly to each other (without going through a Router, which may have security policies applied).If Host A were to craft a malicious packet with a destination MAC address of 0050.7966.6803, despite the switch having this MAC address in it’s MAC Table, since the entry belongs to VLAN 30, the switch will not forward it to Host D. It will instead act as if the switch did not have a matching entry in the MAC table and simply in VLAN 20.