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AT-WR4500 Series - IEEE 802.11abgh Outdoor Wireless Routers 111
RouterOS v3 Configuration and User Guide
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Description
RouterOS has following types of routes:
dynamic routes - automatically created routes for networks, which are directly accessed through an
interface. They appear automatically, when adding a new IP address. Dynamic routes are also added by
routing protocols.
static routes - user-defined routes that specify the router which can forward traffic to the specified
destination network. They are useful for specifying the default gateway. The gateway for static routes may
be checked (with either ARP or ICMP protocol) for reachability, so that different gateways with different
priorities (costs) may be assigned for one destination network to provide failover.
ECMP (Equal Cost Multi-Path) Routing
This routing mechanism enables packet routing along multiple paths with equal cost and ensures load
balancing. With ECMP routing, you can use more than one gateway for one destination network (this
approach may also be configured to provide failover). With ECMP, a router potentially has several
available next hops towards a given destination. A new gateway is chosen for each new source/destination
IP pair. It means that, for example, one FTP connection will use only one link, but new connection to a
different server will use another link. ECMP routing has another good feature - single connection packets
do not get reordered and therefore do not kill TCP performance.
The ECMP routes can be created by routing protocols (RIP or OSPF), or by adding a tatic route with
multiple gateways, separated by a comma (e.g., /ip route add gateway=192.168.0.1,192.168.1.1). The
routing protocols may create multipath dynamic routes with equal cost automatically, if the cost of the
interfaces is adjusted propery. For more information on using routing protocols, please read the
corresponding Manual.
Policy-Based Routing
It is a routing approach where the next hop (gateway) for a packet is chosen, based on a policy, which is
configured by the network administrator. In RouterOS the procedure the follwing:
• mark the desired packets, with a routing-mark
• choose a gateway for the marked packets
In routing process, the router decides which route it will use to send out the packet. Afterwards, when
the packet is masqueraded, its source address is taken from the prefsrc field.
5.4.2 Routes
Submenu level: /ip route
Description
In this submenu you can configure Static, Equal Cost Multi-Path and Policy-Based Routing and see the
routes.
Property Description
bgp-as-path (text) - manual value of BGP's as-path for outgoing route
bgp-atomic-aggregate (yes | no) - indication to receiver that it cannot "deaggregate" the prefix
bgp-communities (multiple choice: integer) - administrative policy marker, that can travel through
different autonomous systems
internet - communities value 0
bgp-local-pref (integer) - local preference value for a route
bgp-med (integer) - a BGP attribute, which provides a mechanism for BGP speakers to convey to an
adjacent AS the optimal entry point into the local AS