Cisco Overlay Transport Virtualization (OTV) is use to connect two or more data centers and extends the VLANs over layer 3, using layer 2 DCI Data center interconnect. It is also called layer 2 VPN over IP.
It supported over any kind of transport, such as point to point , MPLS , Internet , GRE etc.
OTV creates a tunnel over layer 3 connectivity. layer 3 connectivity is called underlay and layer 2 tunnel is called overlay and overlay is use to transfer the layer 2 data.
It supports to both nexus platforms and ASR (ASR 1000). we need to configure it on edge devices.
It does not allow the flooding of spanning-tree , ARP request/reply and icmpv6 nd messages.
OTV uses IS-IS for layer 2 routing and no need to configure IS-IS. because IS-IS is auto configured with OTV. Edge device advertises the MAC addresses and this advertisement of MAC addresses can be control.
Joint interfaces (layer 3) should not be SVI as well as no SVI interface is allow on that VDC. Which is using for OTV.
It does not support the fragmentation. So we should configure the jumbo frames.
Edge Device :- A device running with OTV like ASR 1000 or nexus switch.
AED (Authoritative Edge Device) :- It is an active forwarder adge device for VLANs. It uses the concept of odd/even for load balancing and for loop avoidance.
Site VLAN :- It is a local VLAN. Which is use for syncing control plane information of AEDs. It is also use for electing AED.
Site Identifier :- It is an unique ID per Data center. It will be share with all the AEDs , which belongs from same data center. It helps to prevent the loop and identify the sites.
Overlay Interface :- It is OTV interface.
Joint interface :- Joint interface is layer 3 physical interface. It is use to connect the data centers.
OTV control Group :- It is multicast IP address. Which is use for discovering other OTV sites in the control plane.
OTV data group :- It is use for tunneling unicast traffic over OTV in data plane.
If we are using HSRP at both side AEDs then we should filter the HSRP packets from being pass to other site (data center) , by using VACL and OTV MAC route filtering. Otherwise it can create a problem.
Other DCI Options:
We are having multiple options for configure the DCIs or to connect the multiple data centers.
- Dark Fiber (CWDM , DWDM)
- L2TP3 (layer 2 tunneling protocol version 3) – It is not MPLS dependent. It can work on internet as well. It just requires the IP connectivity.
- ATOM (Any transport Over MPLS) – It is MPLS specific DCI and creates point to point MPLS L2 VPN.
- VPLS – It is point to multipoint MPLS L2 VPN.
Cisco Overlay Transport Virtualization (OTV) Configuration Example:
Conf t int e2/1 no shut ip add 10.1.1.1/24 int e2/2 no shut switchport mode trunk exit vlan 11 , 99 end Conf t feature otv otv site-vlan 99 otv site-identifier 222.222.222 interface overlay 1 otv joint-interface e2/1 int e2/1 ip igmp version 3 mtu 9216 otv overlay 1 otv control-group 126.96.36.199 otv data-group 188.8.131.52/24 otv extended-vlan 11 no shut
Conf t int e2/1 no shut ip add 10.1.1.2/24 int e2/2 no shut switchport mode trunk exit vlan 11 , 99 end Conf t feature otv otv site-vlan 99 otv site-identifier 111.111.111 interface overlay 1 otv joint-interface e2/1 int e2/1 ip igmp version 3 mtu 9216 otv overlay 1 otv control-group 184.108.40.206 otv data-group 220.127.116.11/24 otv extended-vlan 11 no shut
Show otv isis summary show otv show ip arp show mac address-table address AAA:AAA:AAA show otv isis database show mac-address-table vlan 11 show otv adjacency show otv overlay 1 show otv route show otv site show otv statistics show otv anib clients show otv isis internal event-history log
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