ECMP on a Virtual Router
Use the following procedure to enable ECMP on a virtual router. The prerequisites are to:
- Specify the interfaces that belong to a virtual router ().NetworkVirtual RoutersRouter SettingsGeneral
- Specify the IP routing protocol.
Enabling, disabling, or changing ECMP for an existing virtual router causes the system to restart the virtual router, which might cause sessions to be terminated.
- Enable ECMP for a virtual router.
- Selectand select the virtual router on which to enable ECMP.NetworkVirtual Routers
- Selectand selectRouter SettingsECMPEnable.
- (Optional) Enable symmetric return of packets from server to client.(Optional) SelectSymmetric Returnto cause return packets to egress out the same interface on which the associated ingress packets arrived. That is, the firewall will use the ingress interface on which to send return packets, rather than use the ECMP interface. TheSymmetric Returnsetting overrides load balancing. This behavior occurs only for traffic flows from the server to the client.
- Specify the maximum number of equal-cost paths (to a destination network) that can be copied from the Routing Information Base (RIB) to the Forwarding Information Base (FIB).ForMax Pathallowed, enter2,3, or4. Default: 2.
- Select the load-balancing algorithm for the virtual router. For more information on load-balancing methods and how they differ, see ECMP Load-Balancing Algorithms.ForLoad Balance, select one of the following options from theMethoddrop-down:
- IP Modulo(default)—Uses a hash of the source and destination IP addresses in the packet header to determine which ECMP route to use.
- IP Hash—Uses a hash of the source and destination IP addresses and optionally the source and destination port numbers in the packet header to determine which ECMP route to use. Specify options in 5 below.
- Balanced Round Robin—Uses round robin among the ECMP paths and re-balances paths when the number of paths changes.
- Weighted Round Robin—Uses round robin and a relative weight to select from among ECMP paths. Specify the weights in 6 below.
- (IP Hashonly) Configure IP Hash options.If you selectedIP Hashas theMethod:
- SelectUse Source/Destination Portsif you want to use source or destination port numbers in theIP Hashcalculation.
- Enter aHash Seedvalue (an integer with a maximum of nine digits). Specify aHash Seedvalue to further randomize load balancing. Specifying a hash seed value is useful if you have a large number of sessions with the same tuple information.
- (Weighted Round Robinonly) Define a weight for each interface in the ECMP group.If you selectedWeighted Round Robinas theMethod, define a weight for each of the interfaces that are the egress points for traffic to be routed to the same destinations (that is, interfaces that are part of an ECMP group, such as the interfaces that provide redundant links to your ISP or interfaces to the core business applications on your corporate network).The higher the weight, the more often that equal-cost path will be selected for a new session.Give higher speed links a higher weight than a slower links so that more of the ECMP traffic goes over the faster link.
- Create an ECMP group by clickingAddand selecting anInterfacefrom the drop-down.
- Addthe other interfaces in the ECMP group.
- Click onWeightand specify the relative weight for each interface (range is 1-255; default is 100).
- Save the configuration.
- At the ECMP Configuration Change prompt, clickYesto restart the virtual router. Restarting the virtual router might cause existing sessions to be terminated.This message displays only if you are modifying an existing virtual router with ECMP.
- Save the configuration.Committhe configuration.
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