Routing concepts in Cyberoam

Transcription

1 Routing concepts in Cyberoam Article explains routing concepts implemented in Cyberoam, how to define static routes and route policies. It includes following sections: Static route Firewall based routes Destination specific route Policy based route Explicit Source based route Routing order What is routing? Routing is termed as a process of sending packets from network of one device to another network on a different device. Static routes (Destination based routes) A static route is a manually configured mapping of an IP address to a next-hop destination. By default, the Cyberoam routing table contains a single default route. You can add routing information to the routing table by defining additional static routes. Add static routes when you want to route traffic destined for specific network/host via a different next hope instead of a default route. To add static route it is required to know Destination network/host, netmask for destination network & Next hope IP address. The gateway address specifies the next-hop router to which traffic will be routed. A static route causes packets to be forwarded to a different next hope other than the configured default gateway. By specifying through which interface/gateway the packet will leave and to which device the packet should be routed, static routes control the traffic exiting Cyberoam. Example: The following example walks you through the process of creating a static route when Cyberoam is deployed as Gateway. Cyberoam is connected to LAN via switch and configured with multiple links. As Cyberoam is configured with multiple Internet connectivity for load balancing, it will load balance web server traffic via both the gateways Gateway 1 and 2. It is required that all the outbound packets destined to externally hosted wed server should be routed through a particular gateway i.e. Gateway 2 only and not through the Gateway 1. To forward the packets for web server through Gateway 2, we need to define a static route. IP schema Gateway 1: Gateway 2: Web server hosted externally:

2 Configuration: Step 1. Log on to Console through ssh / telnet. Select option 3 Route Configuration in Main Menu to go to the Router Management menu. Step 2. In Route Management, go to option 1 Configure Static-routes/ACLs

3 Enable configuration mode and define static route by executing command from the command prompt as below: router> enable <cr> router# configure terminal router(config)# ip route <destination IP address/netmask> <gateway IP address> for our example, destination IP address is the IP address of the Web server i.e /32 and gateway IP address is the IP address of the gateway through which the requests are to be routed i.e router(config)# write Write command saves the route permanently in the routing table

4 Firewall based route A static route specifies how to handle traffic that matches specific criteria, such as destination address, destination mask, gateway to forward traffic, the interface that gateway is located. Static routing method satisfies most of the requirements, but is limited to forwarding based on destination address only. Firewall based routing is extended static routes which provide more flexible traffic handling capabilities. It allows for matching based upon source address, service/application, and gateway weight for load balancing. Hence, it offers granular control for forwarding packets based upon a number of user defined variables like: Destination Source Application Combination of all of the above The following examples walk through how to create routes with the help of Firewall along with other features. 1. Destination specific route Destination specific route is same as the static route creation except that it is created from firewall page of Web Admin Console while static route is created from Console. Required when: Internal users require access to externally hosted servers Packets for external server should always be routed through a designated gateway and not the default gateway Example: Cyberoam is connected to LAN via switch and configured with multiple links. Mail server is deployed in LAN. LAN user s requests for the externally hosted server should be routed through designated gateway i.e. Gateway 2 only and should not be load balanced. IP schema Gateway 1: Gateway 2: SMTP server (external): Cyberoam WAN IP address: /24 and /24 WAN Alias IP address: Mail server (internal):

5 Step 1: Go to Firewall > Host > Add and define a host i.e. IP address for the external server. You can also add from within the firewall rule as shown in the below given screen shot. Step 2: Go to Firewall > Create Rule to add LAN to WAN rule for the host i.e. external server

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7 2. Policy based route Required when: Server is hosted internally and required to NAT the outbound packets Packets from internal server should always be routed through a designated gateway and should not be load balanced. Example: Cyberoam is connected to LAN via switch and configured with multiple links. Mail server is deployed in LAN. The traffic originated by mail server should be routed through a designated gateway and request should be forwarded with alias IP address i.e. source NATted. IP schema Gateway 1: Gateway 2: Cyberoam WAN IP address: /24 and /24 WAN Alias IP address: Mail server (internal): Configuration: Step 1: Go to Firewall > Host > Add and define a host i.e. IP address for the external server. You can also add from within the firewall rule as shown in the below given screen shot.

8 Step 2. Go to Firewall > SNAT Policy > Create to forward the entire outbound traffic from internal mailer to the specified IP address. For our example, specify WAN Alias IP address Step 3: Go to Firewall > Create Rule to add LAN to WAN rule to forward the mail server traffic to the external server through designated gateway after natting the packets.

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10 Explicit Source based routing from Gateway Required for Half open connections whose information is not available in Cyberoam Example: Mail server hosted internally is used by remote users to send and receive mails and the packets from mail server should explicitly be routed through Gateway 2. IP schema Gateway 1: Gateway 2: Cyberoam WAN IP address: /24 and /24 WAN Alias IP address: Mail server (internal): Configuration: To explicitly route the traffic of a particular host/network from a designated gateway, one has to add host/network under the designated gateway. Step 1: Go to System > Gateway > Manage Gateway(s) and define the all the gateways other than the default gateway. Default gateway is defined at the time of Deployment.

11 Step 2: Go to System > Gateway > Manage Gateway(s) and click the gateway for which host/network is to be added Traffic from the specified host/network will be routed from the selected gateway. Note: If explicit source based routing is not defined then in above mentioned cases, the first return

12 packet (Syn + Ack) from mail server may be routed through either of the gateway, resulting into incomplete 3-way handshake. But incase of TCP packet, firewall maintains session information only when 3-way handshake is complete. Hence it is required to explicitly route such half open connection from the gateway itself. Routing Order Cyberoam provides number of ways to define routes when configured to use multiple gateways. When more than one route is configured, Cyberoam processes route in the following order: 1. Static route (Destination based route) 2. Firewall based routes (Source, Destination or Application based route) 3. Explicit source based route 4. Default Gateway Default gateway is defined at the time of deployment. Document version: /12/2007