Cannot opine about India, but in the US, believe age discrimination is common, although illegal.
Lot's of reasons for this, from the employer's perspective, and it isn't just your salary, but also many other factors related to your "cost" or "benefit" to your employer.
Factors such as: are you more likely to "sick out"? Be more reluctant to work 80 hours weeks (salaried, of course)? Question the actual "grand plan", from on-high, even if you seen same crash-and-burn multiple times, elsewhere, before? Suggest other possible approaches, which weren't invented here (again, which you may have seen work well). Etc.
In addition to the forgoing, when changing career paths, there's often, I believe, some "taint", like what's wrong with you? Couldn't cut it in your prior career?
Basically, there's a reason why militaries like to get recruits at 18, it's not just their energy, but they are often very malleable. Laugh - "there's the right way, the wrong way and the army way".
Now the forgoing doesn't mean starting a fresh career track at 48 is impossible, but although on the "visible" side, you might appear a better choice for the job than a 20 year old candidate, the above "non-visible" considerations often come into play too. Again, it's not impossible, just harder then what it appears it should be.
Certifications, alone, don't get you jobs, especially w/o actual experience, but they can be tie breakers and/or get you into one resume stack, being reviewed, before those without a certificate get reviewed. In many way, much like college degrees, and obtained from where, although not quite the same level of importance.
On the college degree comparison, Cisco certificates would be like a degree from a "name" school and CCNA like an associate degree, a CCNP like a Bachelor's or Master's degree and an CCIE like a Doctor's degree.
It wouldn't hurt to obtain a CCNA, now. If you obtained a CCNP or even CCIE, without any professional work experience, many would think you might only be good at/for passing tests. (A CCNA now, indicates you have good basic networking knowledge; you should be able to perform simple tasks and learn from more experienced network engineers.)
Anyway, again, not impossible, just more difficult than when you're 23 (as if that wasn't hard enough).
Keep trying, make yourself as "attractive" (for the job) as possible, ask for lower salary (then going rate for such a position) because of your inexperience. (Do not mention expecting a salary increase as you gain experience. Either employer will do that, if they recognize your increase in your value, or time to shop for a new position.)
