Dynamic LAN Routing
BGP
The objectives of this deployment are the following:
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high availability: if one hub appliance is in bad health, the other appliance is used as backup appliance |
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load balancing: if your network includes many spokes, you may distribute traffic on several hub appliances |
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transit traffic routing: the two appliances are used to interconnect several regional networks |
iBGP peering is possible:
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between two or more SD-WAN appliances |
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when the SD-WAN appliances have the same AS number |
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when the SD-WAN appliances are connected to the same LAN or VLAN |
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when the SD-WAN appliances are connected to different LANs or VLANs via a Core Router |
This configuration is done on the LAN panel of each appliance.
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Select BGP as the Dynamic LAN Routing Type and the Add Peering function. |
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Enter the IP address of the BGP local peers. |
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Activate AS Path Prepend and enter a value between [1-10]. |
An AS Path is a BGP route attribute and corresponds to the list of autonomous systems that routing information passes through to get to a specified router. AS path length represents the sequence of AS hops that a BGP route follows from a particular AS (the traffic sender) towards the origin AS (the traffic receiver).
For the DWS Service to operate correctly, you can manipulate AS path length by extending the AS path with multiple copies of the AS number of the first AS path hop. For example, by entering 2 as AS Path Prepend value, you define three AS path hops (2 + the initial one) from a Hub to a Spoke for the Internet route. It corresponds to AS_PATH=[65002, 65002, 65002] and is not shorter than AS_PATH=[65500,65002] for the MPLS route (where 65500 represents the MPLS hop).
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Select the Peer SD-WAN appliances. |
OSPF
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Select OSPF as the Dynamic LAN Routing Type. |
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Click the VLAN tab and add VLANs for Routers 1, 2 or 3. Each VLAN corresponds to an OSPF network area. |
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Return to the LAN -> Dynamic LAN Routing -> OSPF page and configure the routers as follows: |
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VLAN: either select the 'None' option to take into account the ip address of the router or another VLAN ID you defined in the previous step. |
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Area ID: by default, Area 0 which is the backbone area or the core of the OSPF network. It corresponds to the area including the CE router. All other areas are connected to it and all the traffic between areas must traverse it. |
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Cost: 10 is the default value. |
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Authentication: for each router, select one authentication method. By default, there is no authentication (NONE option). |
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Key: for each router, enter your authentication password. |
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Key ID: for each router, enter the password identifier value. This value must match the key ID of the Core Router password. |
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Specify OSPF Advanced Settings which are common to all the routers: |
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Hello Timer: time between each Hello packet sent by the router to the interface(s). Hello packets enable the system to establish adjacencies and router keepalive messages to notify neighbors that links are up and active. |
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Dead Timer: time after the last Hello packet is sent by a router and before the router is considered as dead. Dead Timer cannot be smaller than Hello Timer x 3. |
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Priority: with the Broadcast network type (only network type supported), the network elects one Designated Router (DR) and one Backup Designated Router (BDR). They are in charge of transferring topology modifications to all the routers of the area. The priority mechanism determines which router is DR and which one is BDR. |
The router with the highest priority value is the DR router which is the main router for distributing the routes. If both DR and BDR routers have the same priority value, the router with the highest IP address is selected as the DR. With the 0 default value, the router is neither DR nor BDR (it does not participate in the election).
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Default Originate: only check this option if you want to redistribute a default route through OSPF. |
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Instance ID: set this field to 0 to ensure this parameter is not currently used by routers. |
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External Route Cost: implements high availability between two appliances. An external route corresponds to the traffic received by the appliance from the overlay. |
Type 1: the Metric value and the Cost of each link are taken into account to route the traffic.
Cost: this parameter must be configured on your personal routers. Note that a low cost has the priority over a higher cost.
Metric value: this E1 value corresponds to a distance. The lowest value is the best one for routing the traffic.
Type 2: only the Metric value (distance) is taken into account. Set a E2 lower metric value on the Master appliance than on the Backup appliance.
Note: Type 1 takes priority over Type 2.