WISP Design – Building Highly Available VPLS for Public Subnets

What is VPLS?

Virtual Private LAN Service or VPLS is a Layer 2 overlay or tunnel that allows for the encapsulation of ethernet frames (with or without VLAN tags) over an MPLS network.

https://tools.ietf.org/html/rfc4762

VPLS is often found in Telco networks that rely on PPPoE to create centralized BRAS deployments by bringing all of the end users to a common point via L2.

MikroTik VPLS example (https://wiki.mikrotik.com/wiki/Transparently_Bridge_two_Networks_using_MPLS)

Wlink

Background

The idea for this post came out of a working session (at the bar of course) at WISPAmerica 2018 in Birmingham, Alabama.

There was a discussion about how to create redundancy for VPLS tunnels on multiple routers. I started working on this in EVE-NG as we were talking about it.

The goal is creating highly available endpoints for VPLS when using them to deploy a public subnet that can be delivered to any tower in the WISP. The same idea works for wireline networks as well.

Use Case

As IPv4 becomes harder to get, ISPs like WISPs, without large blocks of public space find it difficult to deploy them in smaller subnets. The idea behind breaking up a /23 or /24 for example, is that every tower has public IP addresses available.

However, the problem with this approach is that some subnets may not be used if there isn’t much demand for a dedicated public IP by customers.

What makes VPLS attractive in this scenario is that the public subnet (a /24 in this example) can be placed at the data center as an intact prefix.

VPLS tunnels then allow for individual IP addresses to exist at any tower in the network which provides flexibility and conserves IPv4 space by not subnetting the block into /29 /28 /27 at the tower level.

Lab Network

VPLS

Deployment

In this lab, the VPLS tunnels terminate in two different data centers as well as at a tower router to create an L2 segment for 203.0.113.0/24. VRRP is then run between the two data center VPLS routers so that the gateway of 203.0.113.1 can failover to the other DC if needed.

Failover

Here is an example of the convergence time when we manually fail R1 and the gateway flips over to R2 in the other DC. The yellow highlight marks the point where R1 has failed and R2 VRRP has become master.

vpls-failover

Configurations

R1-vpls-agg

R2-vpls-agg

R3-Tower-1

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Cisco to MikroTik – command translation – OSPF

In the world of network engineering, learning a new syntax for a NOS can be overwhelming if you need a specific set of config in a short timeframe. The command structure for RouterOS can be a bit challenging if you are used to Cisco CLI commands.

If you’ve been in networking for a while, there’s a good chance you started with Cisco gear and so it is helpful to draw comparisons between the commands, especially if you are trying to build a network with a MikroTik and Cisco router.

This is the second post in a series that creates a Rosetta stone essentially between IOS and RouterOS. We plan to tackle  other command comparisons like MPLS, VLANs and basic operations to make it easier for network engineers trained in Cisco IOS to successfully implement Mikrotik / RouterOS devices.

Click here for the first article in this series – “Cisco to MikroTik BGP command translation”

While many commands have almost the exact same information, others are as close as possible. Since there isn’t always an exact match, sometimes you may have to run two or three commands to get the information needed.

Using  EVE-NG for testing

In the last article, we used GNS3 to emulate both Cisco IOS and RouterOS so we could compare the different commands and ensure the translation was as close as possible. For this article, we decided to use EVE-NG as it’s becoming more and more popular for network emulation.

Network for Basic commands

OSPF-topology

 

Cisco commandMikroTik Command
show ip ospf neighborrouting ospf neighbor print
show ip ospf interfacerouting ospf interface print
show ip ospf 1routing ospf instance print detail
show ip ospf databaserouting ospf lsa print
show ip route ospfip route print where ospf=yes
show ip ospf ribrouting ospf route print
show ip ospf border-routersrouting ospf area-border-router print
show ip ospf border-routersrouting ospf as-border-router print
Cisco(config)#router ospf 1/routing ospf instance
Cisco(config-router)#router-id 203.0.113.1/routing ospf instance set 0 router-id=203.0.113.2
Cisco(config-router)#network 203.0.113.1 0.0.0.0 area 0/routing ospf network add area=backbone network=203.0.113.2/32
Cisco(config-router)#network 203.0.113.128 0.0.0.7 area 0/routing ospf network
add area=backbone network=203.0.113.128/29
Cisco(config-router)#interface GigabitEthernet0/0
Cisco(config-if)# ip ospf network point-to-point
Cisco(config-if)# ip ospf dead-interval 4
Cisco(config-if)# ip ospf hello-interval 1
/routing ospf interface add dead-interval=4s hello-interval=1s interface=ether1 network-type=point-to-point

Examples of the MikroTik RouterOS commands from the table above


[admin@MikroTik] > routing ospf neighbor print

This is a quick way to show all the OSPF neighbors the router is adjacent to.

cisco-to-mikrotik-ospf-1

[admin@MikroTik] > routing ospf interface print

This command lists all of the interfaces configured for OSPF, costs, authentication and whether or not the interface is passive. Unlike Cisco, MikroTik’s default behavior is to dynamically create an OPSF interface when a network statement is added which is what the ‘D’ flag stands for.

mikrotik-to-cisco-ospf-interface

[admin@MikroTik] > routing ospf instance print detail

This command lists the details for all OSPF instances on the router including: router-id, redistribution settings, default metrics and filters applied in and out.

cisco-to-mikrotik-ospf-instance-detail

[admin@MikroTik] > routing ospf lsa print

This command lists all OPSF LSAs along with sequence number, originator and age.

cisco-to-mikrotik-ospf-lsa

[admin@MikroTik] > ip route print where ospf=yes

This command allows you to list all of the OSPF routes in the routing table. Unlike Cisco, RouterOS will list routes that aren’t active in the routing table instead of just in the RIB like Cisco.

cisco-to-mikrotik-ospf-ip route-print-where-ospf

[admin@MikroTik] > routing ospf route print

This is a quick way to show the routes that OSPF is aware of on the router, the state of the route, cost and the gateway/interface.

cisco-to-mikrotik-ospf-routing-ospf-route-print

[admin@MikroTik] > routing ospf area-border-router print

Using this command will print all of the ABRs and areas the router is aware of.

cisco-to-mikrotik-ospf-routing-ospf-area-border-router-print

[admin@MikroTik] > routing ospf as-border-router print

This command will list all ASBRs for the router.

cisco-to-mikrotik-ospf-routing-ospf-as-border-router-print

[admin@MikroTik] > routing ospf export

Here is an example of a basic MikroTik OSPF config with a few options turned on like a standard area defined as well as redistribution of connected routes.

cisco-to-mikrotik-ospf-export

More Cisco to MikroTik articles are on the way!

This article covers most of the common OSPF commands. Some of the more advanced config and commands including OSPF flitering, Virtual and Sham Links will be tackled in a separate article. MPLS and VLANs are also on the list. Stay tuned for more!

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