Migrating from Cisco to Juniper


Off late there has been a lot of migration from the traditional Cisco oriented networks to Juniper and Alcatel Lucent. Big organizations have migrated from Cisco to Juniper / Alcatel Lucent respectively and the bidding prices for these projects is between 10-100 millions. However deciding factor for these projects was not price alone but the offerings which Juniper and ALU have in comparison to Cisco.
Some of the nodes which have been replaced are
Cisco 6509 to Juniper EX8200
Cisco 3750 to Juniper 3750
Cisco ASR 9K to Juniper MX960
Cisco Nexus 7000 – Juniper 8200 (Strange?)
We’ll I have been a part of migration from Cisco to Juniper for our access and MPLS core ,so could note down certain things which we had to keep in mind for migration preparation.


1.Use the IOS to JUNOS translator (I2J) tool for converting full IOS configuration files into Juniper JUNOS format –This could save a lot of time if you have a large volume, however the tool still throws up some errors and may point you where manual changes may be required. Also interface mapping is required from corresponding to Cisco.


2. Connectivity issues in layer 2 trunk ports between Cisco and Juniper comes up, when Cisco has UDLD configured at its end .So generally disabling UDLD at the B end cisco device access or distribution layer switch may be required in Juniper/Cisco mixed scenarios.
3. VLAN Difference between Juniper and Cisco Switches
In Cisco switches the default port mode is dynamic desirable auto but in Juniper switch the default port mode is access mode.
In Cisco switches the default VLAN is untagged and is the native VLAN i.e. VLAN 1 but in Juniper there is no default native VLAN. You must configure it manually.
In Cisco switches the trunk ports accept all VLANs in the range of 1 to 4095 by default but in Juniper, trunk ports do not support any VLANs. You have to make it support manually.
In Juniper switches, VLAN named Default is present by default and all the interfaces are under this default VLAN.
Juniper switches has two port modes i.e. access and trunk mode. Cisco switches have five port modes i.e. dynamic auto, dynamic desirable, access, trunk and nonegotiate mode.
Juniper switches support 802.1Q protocol for trunk ports. Cisco switches support both 802.1Q and ISL (Inter Switched Link) protocols.
4. Unlike Cisco switches Juniper switches doesn’t support VTP (VLAN Trunking Protocol) or DTP (Dynamic Trunking Protocol). Juniper switches support GVRP (Generic Attribute Registration Protocol) though.


5.Differences in Administrative distance or preference values have to be taken care of when creating routing policies in Juniper


6. Check if you have proprietary protocols such as HSRP running on the Cisco Boxes ,they may need to be replaced by VRRP.

7. Many enterprises use Weight parameter for load sharing in Dual Homes ISP connectivity. This may have to be changed to local preference.
8.In Junos a router will perform all the functions of an ABR even if there is no Backbone Area 0 .Ex routes between two non-backbone areas will be propagated .However in Cisco the routes between two non-backbone areas will not be propagated unless there is an Area 0 and virtual link becomes mandatory in certain cases.
• By default, CISCO advertises inactive routes – this can be disabled with command “bgp suppress-inactive”, but only in special situations, depending whether next-hop matches or not !
• By default, JUNIPER does not advertise inactive routes – this can be enabled with command “advertise-inactive”
10.If we are using statistics collection in Cisco using Netflow ,that is bundled with the product and does not require additional license.However in JFlow additional module MS-DPC may be required for exporting flow from Juniper devices for higher capacities.
11.Services such as stateful firewall and NAT are supported in Cisco by software off the route processor ,Juniper also does the same but requires MS-DPC functionality ,in that case Backplane capacity may have to be looked into depending about the amount of traffic you want to use into these services.
The above functionalists are just the ones which I encountered in implementation, however underlying differences of Junos versus IOS bring up many differences which should be kept in mind while preparing the LLD for migration.

Happy Migration !


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