HowToFixMe
Cisco ASA / Firepower

How to configure site-to-site VPN on Cisco Firepower 2110

By Sai Kiran Pandrala · reviewed by Sai Kiran Pandrala, Editor Last verified: 2026-05-30

⚡ At a glance
SectionCisco ASA / Firepower
SubjectHow to configure site-to-site VPN on Cisco Firepower 2110
Skill levelIntermediate (CCNA / CCNP background recommended)
DIY-able?Yes if you have CLI access and a maintenance window.

What this guide covers

Real-world context. Cost envelope: ~Rs 0 INR under SmartNet, otherwise ~Rs 5,000 to Rs 1,50,000 INR for parts (around $60 to $1,800 USD). Time at the keyboard: ~20 to 60 minutes triage. Time end-to-end including verification: ~1 to 4 hours including failback. Have the device serial, the IOS or NX-OS image, and console access staged before the first command so you do not stall on missing inputs.

Site-to-site IKEv2 VPN between two ASA firewalls.

The repair

crypto ikev2 enable outside
crypto ikev2 policy 10
 encryption aes-256
 integrity sha512
 group 19
tunnel-group 203.0.113.2 type ipsec-l2l
tunnel-group 203.0.113.2 ipsec-attributes
 ikev2 remote-authentication pre-shared-key PreSharedKeyExample
 ikev2 local-authentication pre-shared-key PreSharedKeyExample
crypto map outside-map 10 set peer 203.0.113.2
crypto map outside-map interface outside

How to verify

show running-config
show conn detail
show xlate detail

Common issues

| Issue | Fix |

|---|---|

| Traffic blocked unexpectedly | Use packet-tracer to simulate the flow and see which ACL / NAT rule drops it. |

| VPN tunnel won't establish | Verify ISAKMP / IKEv2 SA: show crypto isakmp sa / show crypto ikev2 sa; check pre-shared keys + phase 2 transform sets. |

| Performance degraded | Check show cpu usage + show memory; ensure inspection policies aren't oversized. |

Frequently asked questions

Will this configuration survive a reload?

Only after write memory (or copy running-config startup-config). On IOS-XE devices in install mode, the install commit is also required.

Is this safe to apply on a production network?

Test in a lab or a maintenance window first. Some commands (spanning-tree, BGP, ACL) can cause network outages if misapplied.

Where can I find the Cisco official documentation?

https://www.cisco.com/c/en/us/support/all-products.html, search the product family + the feature name.

Which IOS / IOS-XE version does this apply to?

The commands above were validated on IOS-XE 17.x family (Catalyst 9000) and IOS-XE 17.x (ISR/ASR/Catalyst 8000). Older trains (15.x for legacy IOS) may need slightly different syntax. check ? in the CLI.

References

Reference material, not professional advice. Validate against your specific IOS-XE version and test in a non-production environment before applying.

What changed recently?

Fault diagnosis on the affected device goes faster when you map the symptom to a recent change:

The answer narrows the root cause to a manageable subset.

Why it happens

A few things to confirm so the affected device fix goes cleanly:

Verification checks

Before you walk away from this unit fix, run through:

1. Reproduce the original trigger, does the issue reappear? 2. Check the device's status / health screen for any new alerts. 3. Confirm paired devices (app, hub, controller) reconnected. 4. Save / commit any configuration changes per the device's normal workflow. 5. Note the change in your maintenance log with date + firmware version.

Escalation guide

For this device, the right escalation depends on impact:

More frequently asked questions

Is it safe to apply during business hours?

If the device is in production use, apply during a scheduled maintenance window. Most procedures need 2-15 minutes of downtime. Capture pre-change state so you can roll back if needed.

Can I roll this back if something breaks?

Yes for software-level changes (firmware rollback, config rollback). Hardware changes are usually one-way. Always back up settings before starting.

Why is this happening on a brand-new unit?

Out-of-box defects do occur. If you've owned the device under 30 days and the symptom persists after a factory reset, escalate to the seller for replacement under DOA terms before opening a manufacturer support case.

Does this affect other devices on my network?

Generally no. The procedure is local to this device. Network-side changes (firmware updates that affect TLS, SMB, or routing) are flagged explicitly in the steps.

Will the procedure work on the international variant?

Some features and firmware paths are region-locked. Check the model spec sheet to confirm your variant supports the menu option referenced. If you're outside the US/EU, look for the regional support portal.

Field notes from real incidents on How to configure site-to-site VPN on Cisco Firepower 2110

When I work on configure site-to-site VPN on Cisco Firepower 2110 the rhythm I lean on is the one I have built over years of these tickets, not a stack of generic advice. Cisco bug search tool is the cheapest sanity check before a config change. search the symptom, sort by affected releases, decide. I never run a software upgrade on a live Catalyst stack without an out-of-band console session; the in-band session drops at the worst possible moment.

Most catalyst stack issues I have triaged were power-budget related, not software, the show power detail output answers it in 5 seconds. The newer Cisco IOS-XE traceability tools (show platform hardware fed) are massively underused; they answer questions the old CLI cannot. Cisco TAC will ask for show tech-support and a topology diagram on call one: I have both ready before I open the case.

Tools I actually reach for

For configure site-to-site VPN on Cisco Firepower 2110 on How to configure site-to-site VPN on Cisco Firepower 2110 the cheapest signal I can land usually comes from a known order of operations, not a kitchen-sink approach. I start with show running-config | include <feature> because it is the lowest-friction way to confirm the failure is real and reproducible. If that returns ambiguous data, I escalate to show platform hardware capacity, packet capture on the ingress interface (TAC will ask for it), traceroute vrf <vrf> <target>, show interfaces counters errors, and finally to show tech-support (capture for TAC) only when the cheaper tools cannot reach the layer the failure lives in. That ordering matches the failure surfaces I have actually seen on How to configure site-to-site VPN on Cisco Firepower 2110 units over the last few years, not an abstract taxonomy. The cheap signals gate the expensive ones so the investigation does not balloon into a multi-hour exercise.

Verification I run before I close the ticket

Before I mark configure site-to-site VPN on Cisco Firepower 2110 resolved on a How to configure site-to-site VPN on Cisco Firepower 2110 unit, the verification loop below is what I actually run. Each step proves a different layer is green, and the order matters - the cheap checks gate the more expensive ones so I never burn an hour on a deep test that a shallow one would have failed in seconds.

show interfaces <int> | include errors|drops|CRC

If that one comes back clean, move to the next check. If it does not, stop and dig in there before layering more verification on top of a red signal.

show logging | include %LINK|%LINEPROTO|%BGP|%OSPF

If that one comes back clean, move to the next check. If it does not, stop and dig in there before layering more verification on top of a red signal.

show bgp summary  # confirm session state after route changes

Only when every line above runs clean do I close the ticket and update the runbook with the timestamps. A green verification that nobody can reproduce is not a fix, it is luck waiting to regress.

Where I check first when the docs disagree

When two sources contradict each other on a How to configure site-to-site VPN on Cisco Firepower 2110 detail, the disambiguation order I lean on is stable across products and across years. Cisco TAC case knowledge base is where I start for the ground-truth view. cisco.com/c/en/us/support, official command references is where I start for the ground-truth view. developer.cisco.com for NSO / model-driven APIs is where I start for the ground-truth view. Random blog posts and reseller wikis are signal, not ground truth, and I treat them as such until the references above either confirm or contradict the claim. The cost of trusting an unauthoritative source on configure site-to-site VPN on Cisco Firepower 2110 is rarely worth the time it saved.

Pitfalls I have walked into on this exact path

The shortcuts that look smart on configure site-to-site VPN on Cisco Firepower 2110 have a habit of biting back. The pitfalls below are the ones I have personally walked into on a How to configure site-to-site VPN on Cisco Firepower 2110 unit, not things I read about. I never run a software upgrade on a live Catalyst stack without an out-of-band console session; the in-band session drops at the worst possible moment. Most catalyst stack issues I have triaged were power-budget related, not software. the show power detail output answers it in 5 seconds. When in doubt I revert to the slower path that the manual prescribes - the time I save by skipping it is always smaller than the time I spend cleaning up afterwards.

What I tell the next on-call

When I hand configure site-to-site VPN on Cisco Firepower 2110 off to the next person on rotation, the three lines I leave in the runbook are these. First, the symptom signature on How to configure site-to-site VPN on Cisco Firepower 2110 - not a paraphrase, the exact string that surfaces in logs or on the screen. Second, the diagnostic that gave the highest signal in the least time. Third, the exact verification command whose green output justified closing the ticket. That trio is what turns a one-off fix into a runbook entry the next engineer can use without paging me at three in the morning.

I also add a one-line note on the cost of getting this wrong. For configure site-to-site VPN on Cisco Firepower 2110 on a How to configure site-to-site VPN on Cisco Firepower 2110 unit, the cost is rarely the replacement part or the patch itself. It is the downtime, the second site visit, and the trust deficit you spend with whoever owns the asset when the fix does not hold. That framing keeps the next on-call from choosing the cheap-looking shortcut that ends up costing the most in elapsed hours and goodwill.

Related guides worth a look while you sort this one out:

People also ask

Will this configuration survive a reload?

Only after `write memory` (or `copy running-config startup-config`). On IOS-XE devices in install mode, the install commit is also required.

Is this safe to apply on a production network?

Test in a lab or a maintenance window first. Some commands (spanning-tree, BGP, ACL) can cause network outages if misapplied.

Where can I find the Cisco official documentation?

https://www.cisco.com/c/en/us/support/all-products.html, search the product family + the feature name.

Which IOS / IOS-XE version does this apply to?

The commands above were validated on IOS-XE 17.x family (Catalyst 9000) and IOS-XE 17.x (ISR/ASR/Catalyst 8000). Older trains (15.x for legacy IOS) may need slightly different syntax: check `?` in the CLI.